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trunk/paper/CommPhysComp/notes.tex
r523 r525 1 %\documentclass[a4paper,11pt,oneside,twocolumn]{article}2 1 \documentclass[preprint,times,5p,twocolumn]{elsarticle} 3 %\usepackage[english]{babel}4 2 \usepackage[ansinew]{inputenc} 5 %\usepackage{abstract}6 3 7 4 \usepackage{amsmath} … … 34 31 \begin{frontmatter} 35 32 36 \title{ \textsc{Delphes}, a framework for fast simulation of a generic collider experiment}33 \title{Delphes, a framework for fast simulation of a generic collider experiment} 37 34 \author{S. Ovyn\corref{cor1}} 38 35 \ead{severine.ovyn@uclouvain.be} 39 36 40 %\author{X. Rouby\fnref{freiburg}}41 %\fntext[freiburg]{Now in Physikalisches Institut, Albert-Ludwigs-Universit\"at Freiburg}37 \author{X. Rouby\fnref{freiburg}} 38 \fntext[freiburg]{Now in Physikalisches Institut, Albert-Ludwigs-Universit\"at Freiburg} 42 39 %\ead{xavier.rouby@cern.ch} 43 40 44 \address{Center for Particle Physics and Phenomenology (CP3), 45 Universit\'e catholique de Louvain, 41 \author{V. Lema\^itre} 42 43 \address{Center for Particle Physics and Phenomenology (CP3),\\ 44 Universit\'e catholique de Louvain,\\ 46 45 B-1348 Louvain-la-Neuve, Belgium} 47 46 48 \author{X. Rouby}49 \ead{xavier.rouby@cern.ch}50 51 \address{Physikalisches Institut,52 Albert-Ludwigs-Universit\"at Freiburg,53 D-79104 Freiburg-im-Breisgau, Germany}47 %\author{X. Rouby} 48 %\ead{xavier.rouby@cern.ch} 49 50 %\address{Physikalisches Institut, 51 % Albert-Ludwigs-Universit\"at Freiburg, 52 % D-79104 Freiburg-im-Breisgau, Germany} 54 53 55 54 \begin{abstract} 56 55 It is always delicate to know whether theoretical predictions are visible and measurable in a high energy collider experiment due to the complexity of the related detectors, data acquisition chain and software. 57 We introduce here a new \texttt{C++}-based framework, \text sc{Delphes}, for fast simulation of56 We introduce here a new \texttt{C++}-based framework, \textit{Delphes}, for fast simulation of 58 57 a general-purpose experiment. The simulation includes a tracking system, embedded into a magnetic field, calorimetry and a muon 59 58 system, and possible very forward detectors arranged along the beamline. 60 59 The framework is interfaced to standard file formats (e.g.\ Les Houches Event File or \texttt{HepMC}) and outputs observable objects for analysis, like missing transverse energy and collections of electrons or jets. 61 The simulation of detector response takes into account the detector resolution, and usual reconstruction algorithms, such as \textsc{FastJet}. A simplified preselection can also be applied on processed data for trigger emulation. Detection of very forward scattered particles relies on the transport in beamlines with the \textsc{Hector} software. Finally, the \textsc{Frog} 2D/3D event display is used for visualisation of the collision final states.62 An overview of \text sc{Delphes} is given as well as a few \textsc{lhc} use-cases for illustration.\\ \\60 The simulation of detector response takes into account the detector resolution, and usual reconstruction algorithms, such as FastJet. A simplified preselection can also be applied on processed data for trigger emulation. Detection of very forward scattered particles relies on the transport in beamlines with the \textit{Hector} software. Finally, the \textsc{FROG} 2D/3D event display is used for visualisation of the collision final states. 61 An overview of \textit{Delphes} is given as well as a few \textsc{LHC} use-cases for illustration.\\ \\ 63 62 \textit{Preprint:} \texttt{CP3-09-01}, \texttt{arXiv:0903.2225 [hep-ph]}\\ \\ 64 %\includegraphics[scale=0.8]{D elphesLogoSml}\\63 %\includegraphics[scale=0.8]{DELPHESLogoSml}\\ 65 64 \includegraphics[scale=0.8]{fig0}\\ 66 65 {\bf PROGRAM SUMMARY}\\ … … 96 95 {\em External routines/libraries:} ROOT environment \\ 97 96 % Fill in if necessary, otherwise leave out. 98 {\em Subprograms used:} HepMC, S TDHEP, FastJet, Hector, FROG. All provided within DELPHESdistribution. \\97 {\em Subprograms used:} HepMC, StdHEP, FASTJET, \textit{Hector}, FROG. All provided within \textit{Delphes} distribution. \\ 99 98 {\em URL:}\href{http://www.fynu.ucl.ac.be/delphes.html}{http://www.fynu.ucl.ac.be/delphes.html}\\ 100 99 %{\em References:} … … 108 107 109 108 \begin{keyword} 110 \text sc{Delphes} \sep fast simulation \sep trigger \sep event display \sep \textsc{lhc} \sep \textsc{FastJet} \sep \textsc{Hector} \sep \textsc{Frog} \sep Les Houches Event File \sep HepMC \sep \textsc{root}109 \textit{Delphes} \sep fast simulation \sep trigger \sep event display \sep \textsc{LHC} \sep FastJet \sep \textit{Hector} \sep \textsc{FROG} \sep Les Houches Event File \sep HepMC \sep \textsc{ROOT} 111 110 \PACS 29.85.-c \sep 07.05.Tp \sep 29.90.+r \sep 29.50.+v 112 111 \end{keyword} … … 122 121 This complexity is handled by large collaborations of thousands of people, but the data and the expertise are only available to their members. Real data analyses require a full detector simulation, including transport of the primary and secondary particles through the detector material accounting for the various detector inefficiencies, the dead material, the imperfections and the geometrical details. Moreover, control of the detector calibration and alignment are crucial. Such simulation is very complicated, technical and requires a large \texttt{CPU} power. On the other hand, phenomenological studies, looking for the observability of given signals, may require only fast but realistic estimates of the expected signals and associated backgrounds. 123 122 124 A new framework, called \text sc{Delphes}~\citep{bib:Delphes}, is introduced here, for the fast simulation of a general-purpose collider experiment.123 A new framework, called \textit{Delphes}~\citep{bib:delphes}, is introduced here, for the fast simulation of a general-purpose collider experiment. 125 124 Using the framework, observables can be estimated for specific signal and background channels, as well as their production and measurement rates. 126 125 Starting from the output of event generators, the simulation of the detector response takes into account the subdetector resolutions, by smearing the kinematic properties of the final-state particles\footnote{Throughout the paper, final-state particles refer as particles considered as stable by the event generator.}. Tracks of charged particles and deposits of energy in calorimetric cells (or \textit{calotowers}) are then created. 127 126 128 \text sc{Delphes} includes the most crucial experimental features, such as (Fig.~\ref{fig:FlowChart}):127 \textit{Delphes} includes the most crucial experimental features, such as (Fig.~\ref{fig:FlowChart}): 129 128 \begin{enumerate} 130 129 \item the geometry of both central and forward detectors, … … 138 137 \begin{figure*}[!ht] 139 138 \begin{center} 140 %\includegraphics[scale=0.78]{FlowD elphes}139 %\includegraphics[scale=0.78]{FlowDELPHES} 141 140 \includegraphics[scale=0.78]{fig1} 142 \caption{Flow chart describing the principles behind \text sc{Delphes}. Event files coming from external Monte Carlo generators are read by a converter stage (top).141 \caption{Flow chart describing the principles behind \textit{Delphes}. Event files coming from external Monte Carlo generators are read by a converter stage (top). 143 142 The kinematics variables of the final-state particles are then smeared according to the tunable subdetector resolutions. 144 143 Tracks are reconstructed in a simulated solenoidal magnetic field and calorimetric towers sample the energy deposits. Based on these low-level objects, dedicated algorithms are applied for particle identification, isolation and reconstruction. … … 153 152 Although this kind of approach yields much realistic results than a simple ``parton-level" analysis, a fast simulation comes with some limitations. Detector geometry is idealised, being uniform, symmetric around the beam axis, and having no cracks nor dead material. Secondary interactions, multiple scatterings, photon conversion and bremsstrahlung are also neglected. 154 153 155 Four datafile formats can be used as input in \text sc{Delphes}\footnote{\texttt{[code] }See the \texttt{HEPEVTConverter}, \texttt{HepMCConverter}, \texttt{LHEFConverter} and \texttt{STDHEPConverter} classes.}. In order to process events from many different generators, the standard Monte Carlo event structures \texttt{StdHEP}~\citep{bib:stdhep} and \texttt{HepMC}~\citep{bib:hepmc} can be used as an input. Besides, \textsc{Delphes} can also provide detector response for events read in ``Les Houches Event Format'' (\textsc{lhef}~\citep{bib:lhe}) and \textsc{root} files obtained from \textsc{.hbook} using the \texttt{h2root} utility from the \textsc{root} framework~\citep{bib:Root}.156 %Afterwards, \text sc{Delphes} performs a simple trigger simulation and reconstruct "high-level objects". These informations are organised in classes and each objects are ordered with respect to the transverse momentum.157 158 \text sc{Delphes} uses the \texttt{ExRootAnalysis} utility~\citep{bib:ExRootAnalysis} to create output data in a \texttt{*.root} ntuple.159 This output contains a copy of the generator-level data (\text sc{gen} tree), the analysis data objects after reconstruction (\mbox{\textsc{A}nalysis} tree), and possibly the results of the trigger emulation (\mbox{\textsc{T}rigger} tree).160 In option\footnote{\texttt{[code]} See the \texttt{FLAG\_ lhco} variable in the detector datacard. This text file format is shortly described in the user manual.}, \textsc{Delphes} can produce a reduced output file in \texttt{*.lhco} text format, which is limited to the list of the reconstructed high-level objects in the final states.161 162 The program is driven by input cards. The detector card (\texttt{data/DetectorCard.dat}) allows a large spectrum of running conditions by modifying basic detector parameters, including calorimeter and tracking coverage and resolution, thresholds or jet algorithm parameters. The trigger card (\texttt{data/TriggerCard.dat}) lists the user algorithms for the simplified online preselection. Even if \text sc{Delphes} has been developped for the simulation of general-purpose detectors at the \textsc{lhc} (namely, \textsc{cms} and \textsc{atlas}), the input cards allow a flexible parametrisation for other cases, e.g.\ at future linear colliders.154 Four datafile formats can be used as input in \textit{Delphes}\footnote{\texttt{[code] }See the \texttt{HEPEVTConverter}, \texttt{HepMCConverter}, \texttt{LHEFConverter} and \texttt{STDHEPConverter} classes.}. In order to process events from many different generators, the standard Monte Carlo event structures \texttt{StdHEP}~\citep{bib:stdhep} and \texttt{HepMC}~\citep{bib:hepmc} can be used as an input. Besides, \textit{Delphes} can also provide detector response for events read in ``Les Houches Event Format'' (\textsc{LHEF}~\citep{bib:lhe}) and \texttt{*.root} files obtained from \texttt{*.hbook} using the \texttt{h2root} utility from the \textsc{ROOT} framework~\citep{bib:Root}. 155 %Afterwards, \textit{Delphes} performs a simple trigger simulation and reconstruct "high-level objects". These informations are organised in classes and each objects are ordered with respect to the transverse momentum. 156 157 \textit{Delphes} uses the \texttt{ExRootAnalysis} utility~\citep{bib:ExRootAnalysis} to create output data in a \texttt{*.root} ntuple. 158 This output contains a copy of the generator-level data (\texttt{GEN} tree), the analysis data objects after reconstruction (\texttt{Analysis} tree), and possibly the results of the trigger emulation (\texttt{Trigger} tree). 159 In option\footnote{\texttt{[code]} See the \texttt{FLAG\_LHCO} variable in the detector datacard. This text file format is shortly described in the user manual.}, \textit{Delphes} can produce a reduced output file in \texttt{*.LHCO} text format, which is limited to the list of the reconstructed high-level objects in the final states. 160 161 The program is driven by input cards. The detector card (\texttt{data/DetectorCard.dat}) allows a large spectrum of running conditions by modifying basic detector parameters, including calorimeter and tracking coverage and resolution, thresholds or jet algorithm parameters. The trigger card (\texttt{data/TriggerCard.dat}) lists the user algorithms for the simplified online preselection. Even if \textit{Delphes} has been developped for the simulation of general-purpose detectors at the \textsc{LHC} (namely, \textsc{CMS} and \textsc{ATLAS}), the input cards allow a flexible parametrisation for other cases, e.g.\ at future linear colliders. 163 162 164 163 165 164 \section{Detector simulation} 166 165 167 The overall layout of the general-purpose detector simulated by \text sc{Delphes} is shown in Fig.~\ref{fig:GenDet3}.168 A central tracking system (\textsc{ tracker}) is surrounded by an electromagnetic and a hadron calorimeters (\textsc{ecal} and \textsc{hcal}, resp., each with a central region and two endcaps). Two forward calorimeters (\textsc{fcal}) ensure a larger geometric coverage for the measurement of the missing transverse energy. Finally, a muon system (\textsc{muon}) encloses the central detector volume166 The overall layout of the general-purpose detector simulated by \textit{Delphes} is shown in Fig.~\ref{fig:GenDet3}. 167 A central tracking system (\textsc{TRACKER}) is surrounded by an electromagnetic and a hadron calorimeters (\textsc{ECAL} and \textsc{HCAL}, resp., each with a central region and two endcaps). Two forward calorimeters (\textsc{FCAL}) ensure a larger geometric coverage for the measurement of the missing transverse energy. Finally, a muon system (\textsc{MUON}) encloses the central detector volume 169 168 The fast simulation of the detector response takes into account geometrical acceptance of sub-detectors and their finite resolution, as defined in the detector data card\footnote{\texttt{[code] }See the \texttt{RESOLution} class.}. 170 If no such file is provided, predefined values based on ``typical'' \textsc{ cms} acceptances and resolutions are used\footnote{\texttt{[code] }Detector and trigger cards for the \textsc{atlas} and \textsc{cms} experiments are also provided in \texttt{data/} directory.}. The geometrical coverage of the various subsystems used in the default configuration are summarised in Tab.~\ref{tab:defEta}.169 If no such file is provided, predefined values based on ``typical'' \textsc{CMS} acceptances and resolutions are used\footnote{\texttt{[code] }Detector and trigger cards for the \textsc{ATLAS} and \textsc{CMS} experiments are also provided in \texttt{data/} directory.}. The geometrical coverage of the various subsystems used in the default configuration are summarised in Tab.~\ref{tab:defEta}. 171 170 172 171 \begin{table*}[t] … … 178 177 \hline 179 178 Subdetector & & $\eta$ & $\phi$ \\ 180 \textsc{ tracker} & {\verb CEN_max_tracker } & $[-2.5; 2.5]$ & $[-\pi ; \pi]$\\181 \textsc{ ecal}, \textsc{hcal} & {\verb CEN_max_calo_cen }& $[-1.7 ; 1.7]$ & $[-\pi ; \pi]$\\182 \textsc{ ecal}, \textsc{hcal} endcaps & {\verb CEN_max_calo_ec }& $[-3 ; -1.7] \& [1.7 ; 3]$ & $[-\pi ; \pi]$\\183 \textsc{ fcal} & {\verb CEN_max_calo_fwd } & $[-5 ; -3]$ \& $[3 ;5]$ & $[-\pi ; \pi]$\\184 \textsc{ muon} & {\verb CEN_max_mu } & $[-2.4 ; 2.4]$ & $[-\pi ; \pi]$\\ \hline179 \textsc{TRACKER} & {\verb CEN_max_tracker } & $[-2.5; 2.5]$ & $[-\pi ; \pi]$\\ 180 \textsc{ECAL}, \textsc{HCAL} & {\verb CEN_max_calo_cen }& $[-1.7 ; 1.7]$ & $[-\pi ; \pi]$\\ 181 \textsc{ECAL}, \textsc{HCAL} endcaps & {\verb CEN_max_calo_ec }& $[-3 ; -1.7] \& [1.7 ; 3]$ & $[-\pi ; \pi]$\\ 182 \textsc{FCAL} & {\verb CEN_max_calo_fwd } & $[-5 ; -3]$ \& $[3 ;5]$ & $[-\pi ; \pi]$\\ 183 \textsc{MUON} & {\verb CEN_max_mu } & $[-2.4 ; 2.4]$ & $[-\pi ; \pi]$\\ \hline 185 184 \end{tabular} 186 185 \label{tab:defEta} … … 190 189 \begin{figure}[!ht] 191 190 \begin{center} 192 %\includegraphics[width=\columnwidth]{Detector_D elphes_3}191 %\includegraphics[width=\columnwidth]{Detector_DELPHES_3} 193 192 \includegraphics[width=\columnwidth]{fig2} 194 193 \caption{ 195 Profile of layout of the generic detector geometry assumed in \text sc{Delphes}. The innermost layer, close to the interaction point, is a central tracking system (pink).194 Profile of layout of the generic detector geometry assumed in \textit{Delphes}. The innermost layer, close to the interaction point, is a central tracking system (pink). 196 195 It is surrounded by a central calorimeter volume (green) with both electromagnetic and hadronic sections. 197 196 The outer layer of the central system (red) consist of a muon system. In addition, two end-cap calorimeters (blue) extend the pseudorapidity coverage of the central detector. … … 215 214 \subsection{Simulation of central calorimeters} 216 215 217 The energy of each particle considered as stable in the generator particle list is smeared, with a Gaussian distribution depending on the calorimeter resolution. This resolution varies with the sub-calorimeter (\textsc{ ecal}, \textsc{hcal}, \textsc{fcal}) measuring the particle.216 The energy of each particle considered as stable in the generator particle list is smeared, with a Gaussian distribution depending on the calorimeter resolution. This resolution varies with the sub-calorimeter (\textsc{ECAL}, \textsc{HCAL}, \textsc{FCAL}) measuring the particle. 218 217 The response of each sub-calorimeter is parametrised as a function of the energy: 219 218 \begin{equation} … … 226 225 The particle four-momentum $p^\mu$ are smeared with a parametrisation directly derived from typical detector technical designs\footnote{\texttt{[code] } The response of the detector is applied to the electromagnetic and the hadronic particles through the \texttt{SmearElectron} and \texttt{SmearHadron} functions.} \citep{bib:cmsjetresolution,bib:ATLASresolution}. 227 226 In the default parametrisation, the calorimeter is assumed to cover the pseudorapidity range $|\eta|<3$ and consists in an electromagnetic and hadronic parts. Coverage between pseudorapidities of $3.0$ and $5.0$ is provided by forward calorimeters, with different response to electromagnetic objects ($e^\pm, \gamma$) or hadrons. 228 Muons and neutrinos are assumed not to interact with the calorimeters\footnote{In the current \text sc{Delphes} version, particles other than electrons ($e^\pm$), photons ($\gamma$), muons ($\mu^\pm$) and neutrinos ($\nu_e$, $\nu_\mu$ and $\nu_\tau$) are simulated as hadrons for their interactions with the calorimeters. The simulation of stable particles beyond the Standard Model should therefore be handled with care.}.227 Muons and neutrinos are assumed not to interact with the calorimeters\footnote{In the current \textit{Delphes} version, particles other than electrons ($e^\pm$), photons ($\gamma$), muons ($\mu^\pm$) and neutrinos ($\nu_e$, $\nu_\mu$ and $\nu_\tau$) are simulated as hadrons for their interactions with the calorimeters. The simulation of stable particles beyond the Standard Model should therefore be handled with care.}. 229 228 The default values of the stochastic, noise and constant terms are given in Tab.~\ref{tab:defResol}.\\ 230 229 … … 236 235 \hline 237 236 \multicolumn{2}{c}{Resolution Term} & Card flag & Value\\\hline 238 \multicolumn{4}{l}{\textsc{ ecal}} \\237 \multicolumn{4}{l}{\textsc{ECAL}} \\ 239 238 & $S$ (GeV$^{1/2}$) & {\verb ELG_Scen } & $0.05$ \\ 240 239 & $N$ (GeV)& {\verb ELG_Ncen } & $0.25$ \\ 241 240 & $C$ & {\verb ELG_Ccen } & $0.0055$ \\ 242 \multicolumn{4}{l}{\textsc{ ecal}, end caps} \\241 \multicolumn{4}{l}{\textsc{ECAL}, end caps} \\ 243 242 & $S$ (GeV$^{1/2}$) & {\verb ELG_Sec } & $0.05$ \\ 244 243 & $N$ (GeV)& {\verb ELG_Nec } & $0.25$ \\ 245 244 & $C$ & {\verb ELG_Cec } & $0.0055$ \\ 246 \multicolumn{4}{l}{\textsc{ fcal}, electromagnetic part} \\245 \multicolumn{4}{l}{\textsc{FCAL}, electromagnetic part} \\ 247 246 & $S$ (GeV$^{1/2}$)& {\verb ELG_Sfwd } & $2.084$ \\ 248 247 & $N$ (GeV)& {\verb ELG_Nfwd } & $0$ \\ 249 248 & $C$ & {\verb ELG_Cfwd } & $0.107$ \\ 250 \multicolumn{4}{l}{\textsc{ hcal}} \\249 \multicolumn{4}{l}{\textsc{HCAL}} \\ 251 250 & $S$ (GeV$^{1/2}$)& {\verb HAD_Scen } & $1.5$ \\ 252 251 & $N$ (GeV)& {\verb HAD_Ncen } & $0$\\ 253 252 & $C$ & {\verb HAD_Ccen } & $0.05$\\ 254 \multicolumn{4}{l}{\textsc{ hcal}, end caps} \\253 \multicolumn{4}{l}{\textsc{HCAL}, end caps} \\ 255 254 & $S$ (GeV$^{1/2}$)& {\verb HAD_Sec } & $1.5$ \\ 256 255 & $N$ (GeV)& {\verb HAD_Nec } & $0$\\ 257 256 & $C$ & {\verb HAD_Cec } & $0.05$\\ 258 \multicolumn{4}{l}{\textsc{ fcal}, hadronic part} \\257 \multicolumn{4}{l}{\textsc{FCAL}, hadronic part} \\ 259 258 & $S$ (GeV$^{1/2}$)& {\verb HAD_Sfwd } & $2.7$\\ 260 259 & $N$ (GeV)& {\verb HAD_Nfwd } & $0$ \\ … … 266 265 \end{table} 267 266 268 The energy of electrons and photons found in the particle list are smeared using the \textsc{ ecal} resolution terms. Charged and neutral final-state hadrons interact with the \textsc{ecal}, \textsc{hcal} and \textsc{fcal}.269 Some long-living particles, such as the $K^0_s$ and $\Lambda$'s, with lifetime $c\tau$ smaller than $10~\textrm{mm}$ are considered as stable particles although they decay before the calorimeters. The energy smearing of such particles is performed using the expected fraction of the energy, determined according to their decay products, that would be deposited into the \textsc{ ecal} ($E_{\textsc{ecal}}$) and into the \textsc{hcal} ($E_{\textsc{hcal}}$). Defining $F$ as the fraction of the energy leading to a \textsc{hcal} deposit, the two energy values are given by267 The energy of electrons and photons found in the particle list are smeared using the \textsc{ECAL} resolution terms. Charged and neutral final-state hadrons interact with the \textsc{ECAL}, \textsc{HCAL} and \textsc{FCAL}. 268 Some long-living particles, such as the $K^0_s$ and $\Lambda$'s, with lifetime $c\tau$ smaller than $10~\textrm{mm}$ are considered as stable particles although they decay before the calorimeters. The energy smearing of such particles is performed using the expected fraction of the energy, determined according to their decay products, that would be deposited into the \textsc{ECAL} ($E_{\textsc{ECAL}}$) and into the \textsc{HCAL} ($E_{\textsc{HCAL}}$). Defining $F$ as the fraction of the energy leading to a \textsc{HCAL} deposit, the two energy values are given by 270 269 \begin{equation} 271 270 \left\{ 272 271 \begin{array}{l} 273 E_{\textsc{ hcal}} = E \times F \\274 E_{\textsc{ ecal}} = E \times (1-F) \\272 E_{\textsc{HCAL}} = E \times F \\ 273 E_{\textsc{ECAL}} = E \times (1-F) \\ 275 274 \end{array} 276 275 \right. 277 276 \end{equation} 278 277 where $0 \leq F \leq 1$. The electromagnetic part is handled the same way for the electrons and photons. 279 The resulting calorimetry energy measurement given after the application of the smearing is then $E = E_{\textsc{ hcal}} + E_{\textsc{ecal}}$. For $K_S^0$ and $\Lambda$ hadrons\footnote{\texttt{[code]} To implement different ratios for other particles, see the \texttt{BlockClasses} class.}, the energy fraction is $F$ is assumed to be $0.7$.\\278 The resulting calorimetry energy measurement given after the application of the smearing is then $E = E_{\textsc{HCAL}} + E_{\textsc{ECAL}}$. For $K_S^0$ and $\Lambda$ hadrons\footnote{\texttt{[code]} To implement different ratios for other particles, see the \texttt{BlockClasses} class.}, the energy fraction is $F$ is assumed to be $0.7$.\\ 280 279 281 280 \subsection{Calorimetric towers} 282 281 283 The smallest unit for geometrical sampling of the calorimeters is a \textit{tower}; it segments the $(\eta,\phi)$ plane for the energy measurement. No longitudinal segmentation is available in the simulated calorimeters. All undecayed particles, except muons and neutrinos deposit energy in a calorimetric tower, either in \textsc{ ecal}, in \textsc{hcal} or \textsc{fcal}.282 The smallest unit for geometrical sampling of the calorimeters is a \textit{tower}; it segments the $(\eta,\phi)$ plane for the energy measurement. No longitudinal segmentation is available in the simulated calorimeters. All undecayed particles, except muons and neutrinos deposit energy in a calorimetric tower, either in \textsc{ECAL}, in \textsc{HCAL} or \textsc{FCAL}. 284 283 As the detector is assumed to be cylindrical (e.g.\ symmetric in $\phi$ and with respect to the $\eta=0$ plane), the detector card stores the number of calorimetric towers with $\phi=0$ and $\eta>0$ (default: $40$ towers). For a given $\eta$, the size of the $\phi$ segmentation is also specified. Fig.~\ref{fig:calosegmentation} illustrates the default calorimeter segmentation, which is common for the electromagnetic and hadronic sections at a given $(\eta,\phi)$. 285 284 … … 288 287 %\includegraphics[width=\columnwidth]{calosegmentation} 289 288 \includegraphics[width=\columnwidth]{fig3} 290 \caption{Default segmentation of the calorimeters in the $(\eta,\phi)$ plane. Only the central detectors (\textsc{ ecal}, \textsc{hcal}) and \textsc{fcal} are considered. $\phi$ angles are expressed in radians.}289 \caption{Default segmentation of the calorimeters in the $(\eta,\phi)$ plane. Only the central detectors (\textsc{ECAL}, \textsc{HCAL}) and \textsc{FCAL} are considered. $\phi$ angles are expressed in radians.} 291 290 \label{fig:calosegmentation} 292 291 \end{center} 293 292 \end{figure} 294 293 295 The calorimetric towers directly enter in the calculation of the missing transverse energy (\textsc{ met}), and as input for the jet reconstruction algorithms. No sharing between neighbouring towers is implemented when particles enter a tower very close to its geometrical edge. Smearing is applied directly on the accumulated electromagnetic and hadronic energies of each calorimetric tower.294 The calorimetric towers directly enter in the calculation of the missing transverse energy (\textsc{MET}), and as input for the jet reconstruction algorithms. No sharing between neighbouring towers is implemented when particles enter a tower very close to its geometrical edge. Smearing is applied directly on the accumulated electromagnetic and hadronic energies of each calorimetric tower. 296 295 297 296 \subsection{Very forward detector simulation} 298 297 299 Most of the recent experiments in beam colliders have additional instrumentation along the beamline. These extend the $\eta$ coverage to higher values, for the detection of very forward final-state particles. In \text sc{Delphes}, Zero Degree Calorimeters, roman pots and forward taggers have been implemented (Fig.~\ref{fig:fdets}).298 Most of the recent experiments in beam colliders have additional instrumentation along the beamline. These extend the $\eta$ coverage to higher values, for the detection of very forward final-state particles. In \textit{Delphes}, Zero Degree Calorimeters, roman pots and forward taggers have been implemented (Fig.~\ref{fig:fdets}). 300 299 301 300 \begin{figure}[!ht] … … 303 302 %\includegraphics[width=\columnwidth]{fdets} 304 303 \includegraphics[width=\columnwidth]{fig4} 305 \caption{Default location of the very forward detectors, including \textsc{ zdc}, \textsc{rp220} and \textsc{fp420} in the \textsc{lhc} beamline.306 Incoming (beam 1, red) and outgoing (beam 2, black) beams on one side of the fifth interaction point (\textsc{ ip}5, $s=0~\textrm{m}$ on the plot).307 The Zero Degree Calorimeter is located in perfect alignment with the beamline axis at the interaction point, at $140~\textrm{m}$, the beam paths are separated. The forward taggers are near-beam detectors located at $220~\textrm{m}$ and $420~\textrm{m}$. Beamline simulation with \text sc{Hector}~\citep{bib:Hector}. All very forward detectors are located symmetrically around the interaction point. }304 \caption{Default location of the very forward detectors, including \textsc{ZDC}, \textsc{RP220} and \textsc{FP420} in the \textsc{LHC} beamline. 305 Incoming (beam 1, red) and outgoing (beam 2, black) beams on one side of the fifth interaction point (\textsc{IP5}, $s=0~\textrm{m}$ on the plot). 306 The Zero Degree Calorimeter is located in perfect alignment with the beamline axis at the interaction point, at $140~\textrm{m}$, the beam paths are separated. The forward taggers are near-beam detectors located at $220~\textrm{m}$ and $420~\textrm{m}$. Beamline simulation with \textit{Hector}~\citep{bib:hector}. All very forward detectors are located symmetrically around the interaction point. } 308 307 \label{fig:fdets} 309 308 \end{center} … … 312 311 \begin{table*}[t] 313 312 \begin{center} 314 \caption{Default parameters for the forward detectors: distance from the interaction point and detector acceptance. The \textsc{ lhc} beamline is assumed around the fifth \textsc{lhc} interaction point (\textsc{ip}). For the \textsc{zdc}, the acceptance depends only on the pseudorapidity $\eta$ of the particle, which should be neutral and stable.315 The tagger acceptance is fully determined by the distance in the transverse plane of the detector to the real beam position~\citep{bib: Hector}. It is expressed in terms of the particle energy ($E$).313 \caption{Default parameters for the forward detectors: distance from the interaction point and detector acceptance. The \textsc{LHC} beamline is assumed around the fifth \textsc{LHC} interaction point (\textsc{IP}). For the \textsc{ZDC}, the acceptance depends only on the pseudorapidity $\eta$ of the particle, which should be neutral and stable. 314 The tagger acceptance is fully determined by the distance in the transverse plane of the detector to the real beam position~\citep{bib:hector}. It is expressed in terms of the particle energy ($E$). 316 315 All detectors are located on both sides of the interaction point. 317 316 \vspace{0.5cm}} 318 317 \begin{tabular}{llcl} 319 318 \hline 320 Detector & Distance from \textsc{ ip}& Acceptance & \\ \hline321 \textsc{ zdc} & $\pm 140$ m & $|\eta|> 8.3$ & for $n$ and $\gamma$\\322 \textsc{ rp220} & $\pm 220$ m & $E \in [6100 ; 6880]$ (GeV) & at $2~\textrm{mm}$\\323 \textsc{ fp420} & $\pm 420$ m & $E \in [6880 ; 6980]$ (GeV) & at $4~\textrm{mm}$\\319 Detector & Distance from \textsc{IP}& Acceptance & \\ \hline 320 \textsc{ZDC} & $\pm 140$ m & $|\eta|> 8.3$ & for $n$ and $\gamma$\\ 321 \textsc{RP220} & $\pm 220$ m & $E \in [6100 ; 6880]$ (GeV) & at $2~\textrm{mm}$\\ 322 \textsc{FP420} & $\pm 420$ m & $E \in [6880 ; 6980]$ (GeV) & at $4~\textrm{mm}$\\ 324 323 \hline 325 324 \end{tabular} … … 331 330 \subsubsection*{Zero Degree Calorimeters} 332 331 333 In direct sight of the interaction point, on both sides of the central detector, the Zero Degree Calorimeters (\textsc{ zdc}s) are located at zero angle, i.e.\ are aligned with the beamline axis at the interaction point. They are placed beyond the point where the paths of incoming and outgoing beams separate. These allow the measurement of stable neutral particles ($\gamma$ and $n$) coming from the interaction point, with large pseudorapidities (e.g.\ $|\eta_{\textrm{n,}\gamma}| > 8.3$ in \textsc{atlas} and \textsc{cms}).334 335 The trajectory of the neutrals observed in the \textsc{ zdc}s is a straight line, while charged particles are deflected away from their acceptance window by the powerful magnets located in front of them. The fact that additional charged particles may enter the \textsc{zdc} acceptance is neglected here.336 337 The \textsc{ zdc}s have the ability to measure the time-of-flight of the particle.332 In direct sight of the interaction point, on both sides of the central detector, the Zero Degree Calorimeters (\textsc{ZDC}s) are located at zero angle, i.e.\ are aligned with the beamline axis at the interaction point. They are placed beyond the point where the paths of incoming and outgoing beams separate. These allow the measurement of stable neutral particles ($\gamma$ and $n$) coming from the interaction point, with large pseudorapidities (e.g.\ $|\eta_{\textrm{n,}\gamma}| > 8.3$ in \textsc{ATLAS} and \textsc{CMS}). 333 334 The trajectory of the neutrals observed in the \textsc{ZDC}s is a straight line, while charged particles are deflected away from their acceptance window by the powerful magnets located in front of them. The fact that additional charged particles may enter the \textsc{ZDC} acceptance is neglected here. 335 336 The \textsc{ZDC}s have the ability to measure the time-of-flight of the particle. 338 337 This corresponds to the delay after which the particle is observed in the detector, with respect to the bunch crossing reference time at the interaction point ($t_0$). The measured time-of-flight $t$ is simply given by: 339 338 \begin{equation} 340 339 t = t_0 + \frac{1}{v} \times \Big( \frac{s-z}{\cos \theta}\Big), 341 340 \end{equation} 342 where $t_0$ is thus the true time coordinate of the vertex from which the particle originates, $v$ the particle velocity, $s$ is the \textsc{ zdc} distance to the interaction point, $z$ is the longitudinal coordinate of the vertex, $\theta$ is the particle emission angle. It is then assumed that the neutral particle observed in the \textsc{zdc} is highly relativistic, i.e.\ travelling at the speed of light $c$. We also assume that $\cos \theta = 1$, i.e.\ $\theta \approx 0$ or equivalently $\eta$ is large. As an example, $\eta = 5$ leads to $\theta = 0.013$ and $1 - \cos \theta < 10^{-4}$.341 where $t_0$ is thus the true time coordinate of the vertex from which the particle originates, $v$ the particle velocity, $s$ is the \textsc{ZDC} distance to the interaction point, $z$ is the longitudinal coordinate of the vertex, $\theta$ is the particle emission angle. It is then assumed that the neutral particle observed in the \textsc{ZDC} is highly relativistic, i.e.\ travelling at the speed of light $c$. We also assume that $\cos \theta = 1$, i.e.\ $\theta \approx 0$ or equivalently $\eta$ is large. As an example, $\eta = 5$ leads to $\theta = 0.013$ and $1 - \cos \theta < 10^{-4}$. 343 342 The formula then reduces to 344 343 \begin{equation} 345 344 t = \frac{1}{c} \times (s-z). 346 345 \end{equation} 347 For example, a photon takes $0.47~\mu\textrm{s}$ to reach a \textsc{ zdc} located at $s=140~\textrm{m}$, neglecting $z$ and $\theta$. For the time-of-flight measurement, a Gaussian smearing can be applied according to the detector resolution (Tab.~\ref{tab:defResolZdc}). In the current version of \textsc{Delphes}, only neutrons, antineutrons and photons are assumed to be able to reach the \textsc{zdc}s, all other particles being neglected.348 349 The \textsc{ zdc}s are composed of an electromagnetic and a hadronic sections, for the measurement of photons and neutrons, respectively. The energy of the observed neutral is smeared according to Eq.~\ref{eq:caloresolution} and the corresponding section resolutions (Tab.~\ref{tab:defResolZdc}). The \textsc{zdc} hits do not enter in the calorimeter tower list used for reconstruction of jets and missing transverse energy.346 For example, a photon takes $0.47~\mu\textrm{s}$ to reach a \textsc{ZDC} located at $s=140~\textrm{m}$, neglecting $z$ and $\theta$. For the time-of-flight measurement, a Gaussian smearing can be applied according to the detector resolution (Tab.~\ref{tab:defResolZdc}). In the current version of \textit{Delphes}, only neutrons, antineutrons and photons are assumed to be able to reach the \textsc{ZDC}s, all other particles being neglected. 347 348 The \textsc{ZDC}s are composed of an electromagnetic and a hadronic sections, for the measurement of photons and neutrons, respectively. The energy of the observed neutral is smeared according to Eq.~\ref{eq:caloresolution} and the corresponding section resolutions (Tab.~\ref{tab:defResolZdc}). The \textsc{ZDC} hits do not enter in the calorimeter tower list used for reconstruction of jets and missing transverse energy. 350 349 351 350 \begin{table}[!h] … … 356 355 \hline 357 356 \multicolumn{2}{c}{Resolution Term} & Card flag & Value\\\hline 358 \multicolumn{4}{l}{\textsc{ zdc}, electromagnetic part} \\357 \multicolumn{4}{l}{\textsc{ZDC}, electromagnetic part} \\ 359 358 & $S$ (GeV$^{1/2}$)& \texttt{ELG\_Szdc} & $0.7$ \\ 360 359 & $N$ (GeV)& \texttt{ELG\_Nzdc} & $0.0$ \\ 361 360 & $C$ & \texttt{ELG\_Czdc} & $0.08$ \\ 362 \multicolumn{4}{l}{\textsc{ zdc}, hadronic part} \\361 \multicolumn{4}{l}{\textsc{ZDC}, hadronic part} \\ 363 362 & $S$ (GeV$^{1/2}$)& \texttt{HAD\_Szdc} & $1.38$\\ 364 363 & $N$ (GeV)& \texttt{HAD\_Nzdc} & $0$ \\ 365 364 & $C$ & \texttt{HAD\_Czdc} & $0.13$\\ 366 \multicolumn{4}{l}{\textsc{ zdc}, timing resolution} \\365 \multicolumn{4}{l}{\textsc{ZDC}, timing resolution} \\ 367 366 & $\sigma_t$ (s) & \texttt{ZDC\_T\_resolution} & $0$ \\ 368 367 \hline … … 374 373 \subsubsection*{Forward taggers} 375 374 376 Forward taggers (called here \textsc{ rp220}, for ``roman pots at $220~\textrm{m}$'' and \textsc{fp420} ``for forward proton taggers at $420~\textrm{m}$'', as at the \textsc{lhc}) are meant for the measurement of particles following very closely the beam path. Such devices, also used at \textsc{hera} and \textsc{Tevratron}, are located very far away from the interaction point (further than $150$~m in the \textsc{lhc} case).375 Forward taggers (called here \textsc{RP220}, for ``roman pots at $220~\textrm{m}$'' and \textsc{FP420} ``for forward proton taggers at $420~\textrm{m}$'', as at the \textsc{LHC}) are meant for the measurement of particles following very closely the beam path. Such devices, also used at \textsc{HERA} and Tevatron, are located very far away from the interaction point (further than $150$~m in the \textsc{LHC} case). 377 376 378 377 To be able to reach these detectors, particles must have a charge identical to the beam particles, and a momentum very close to the nominal value of the beam. These taggers are near-beam detectors located a few millimetres from the true beam trajectory and this distance defines their acceptance (Tab.~\ref{tab:fdetacceptance}). 379 For instance, roman pots at $220~\textrm{m}$ from the \textsc{ ip} and $2~\textrm{mm}$ from the beam will detect all forward protons with an energy between $120$ and $900~\textrm{GeV}$~\citep{bib:Hector}.380 In practice, in the \textsc{ lhc}, only positively charged muons ($\mu^+$) and protons can reach the forward taggers as other particles with a single positive charge coming from the interaction points will decay before their possible tagging. In \textsc{Delphes}, extra hits coming from the beam-gas events or secondary particles hitting the beampipe in front of the detectors are not taken into account.381 382 While neutral particles propagate along a straight line to the \textsc{ zdc}, a dedicated simulation of the transport of charged particles is needed for \textsc{rp220} and \textsc{fp420}. This fast simulation uses the \textsc{Hector} software~\citep{bib:Hector}, which includes the chromaticity effects and the geometrical aperture of the beamline elements of any arbitrary collider.383 384 Forward taggers are able to measure the hit positions ($x,y$) and angles ($\theta_x,\theta_y$) in the transverse plane at the location of the detector ($s$ meters away from the \textsc{ ip}), as well as the time-of-flight\footnote{It should be noted that for both \textsc{cms} and \textsc{atlas} experiments, the taggers located at $220$~m are not able to measure the time-of-flight, contrary to \textsc{fp}420 detectors.} ($t$). Out of these the particle energy ($E$) and the momentum transfer it underwent during the interaction ($q^2$) can be reconstructed\footnote{The reconstruction of $E$ and $q^2$ are not implemeted in \textsc{Delphes} but can be performed at the analysis level.}. The time-of-flight measurement can be smeared with a Gaussian distribution (default value\footnote{\texttt{[code] } The resolution is defined by the \texttt{RP220\_T\_resolution} and \texttt{RP420\_T\_resolution} parameters in the detector card.} $\sigma_t = 0~\textrm{s}$).378 For instance, roman pots at $220~\textrm{m}$ from the \textsc{IP} and $2~\textrm{mm}$ from the beam will detect all forward protons with an energy between $120$ and $900~\textrm{GeV}$~\citep{bib:hector}. 379 In practice, in the \textsc{LHC}, only positively charged muons ($\mu^+$) and protons can reach the forward taggers as other particles with a single positive charge coming from the interaction points will decay before their possible tagging. In \textit{Delphes}, extra hits coming from the beam-gas events or secondary particles hitting the beampipe in front of the detectors are not taken into account. 380 381 While neutral particles propagate along a straight line to the \textsc{ZDC}, a dedicated simulation of the transport of charged particles is needed for \textsc{RP220} and \textsc{FP420}. This fast simulation uses the \textit{Hector} software~\citep{bib:hector}, which includes the chromaticity effects and the geometrical aperture of the beamline elements of any arbitrary collider. 382 383 Forward taggers are able to measure the hit positions ($x,y$) and angles ($\theta_x,\theta_y$) in the transverse plane at the location of the detector ($s$ meters away from the \textsc{IP}), as well as the time-of-flight\footnote{It should be noted that for both \textsc{CMS} and \textsc{ATLAS} experiments, the taggers located at $220$~m are not able to measure the time-of-flight, contrary to \textsc{FP420} detectors.} ($t$). Out of these the particle energy ($E$) and the momentum transfer it underwent during the interaction ($q^2$) can be reconstructed\footnote{The reconstruction of $E$ and $q^2$ are not implemeted in \textit{Delphes} but can be performed at the analysis level.}. The time-of-flight measurement can be smeared with a Gaussian distribution (default value\footnote{\texttt{[code] } The resolution is defined by the \texttt{RP220\_T\_resolution} and \texttt{RP420\_T\_resolution} parameters in the detector card.} $\sigma_t = 0~\textrm{s}$). 385 384 386 385 … … 388 387 \section{High-level object reconstruction} 389 388 390 Analysis object data contain the final collections of particles ($e^\pm$, $\mu^\pm$, $\gamma$) or objects (light jets, $b$-jets, $\tau$-jets, $E_T^\textrm{miss}$) and are stored\footnote{\texttt{[code] }All these processed data are located under the \texttt{Analysis} tree.} in the output file created by \text sc{Delphes}.391 In addition, some detector data are added: tracks, calorimetric towers and hits in \textsc{ zdc}, \textsc{rp220} and \textsc{fp420}.389 Analysis object data contain the final collections of particles ($e^\pm$, $\mu^\pm$, $\gamma$) or objects (light jets, $b$-jets, $\tau$-jets, $E_T^\textrm{miss}$) and are stored\footnote{\texttt{[code] }All these processed data are located under the \texttt{Analysis} tree.} in the output file created by \textit{Delphes}. 390 In addition, some detector data are added: tracks, calorimetric towers and hits in \textsc{ZDC}, \textsc{RP220} and \textsc{FP420}. 392 391 While electrons, muons and photons are easily identified, some other objects are more difficult to measure, like jets or missing energy due to invisible particles. 393 392 394 For most of these objects, their four-momentum and related quantities are directly accessible in \text sc{Delphes} output ($E$, $\vec{p}$, $p_T$, $\eta$ and $\phi$). Additional properties are available for specific objects (like the charge and the isolation status for $e^\pm$ and $\mu^\pm$, the result of application of $b$-tag for jets and time-of-flight for some detector hits).393 For most of these objects, their four-momentum and related quantities are directly accessible in \textit{Delphes} output ($E$, $\vec{p}$, $p_T$, $\eta$ and $\phi$). Additional properties are available for specific objects (like the charge and the isolation status for $e^\pm$ and $\mu^\pm$, the result of application of $b$-tag for jets and time-of-flight for some detector hits). 395 394 396 395 … … 401 400 \subsubsection*{Electrons and photons} 402 401 Electron ($e^\pm$) and photon candidates are reconstructed if they fall into the acceptance of the tracking system and have a transverse momentum above a threshold (default $p_T > 10~\textrm{GeV}/c$). A calorimetric tower will be seen in the detector, as electrons will leave in addition a track. Subsequently, electrons and photons create a candidate in the jet collection. 403 Assuming a good measurement of the track parameters in the real experiment, the electron energy can be reasonably recovered. In \text sc{Delphes}, electron energy is smeared according to the resolution of the calorimetric tower where it points to, but independently from any other deposited energy is this tower. This approach is still conservative as the calorimeter resolution is worse than the tracker one.402 Assuming a good measurement of the track parameters in the real experiment, the electron energy can be reasonably recovered. In \textit{Delphes}, electron energy is smeared according to the resolution of the calorimetric tower where it points to, but independently from any other deposited energy is this tower. This approach is still conservative as the calorimeter resolution is worse than the tracker one. 404 403 405 404 \subsubsection*{Muons} 406 405 Generator-level muons entering the detector acceptance are considered as candidates for the analysis level. 407 406 The acceptance is defined in terms of a transverse momentum threshold to be overpassed that should be computed using the chosen geometry of the detector and the magnetic field considered (default : $p_T > 10~\textrm{GeV}/c$) and of the pseudorapidity coverage of the muon system (default: $-2.4 \leq \eta \leq 2.4$). 408 The application of the detector resolution on the muon momentum depends on a Gaussian smearing of the $p_T$ variable\footnote{\texttt{[code]} See the \texttt{SmearMuon} method.}. Neither $\eta$ nor $\phi$ variables are modified beyond the calorimeters: no additional magnetic field is applied. Multiple scattering is neglected. This implies that low energy muons have in \text sc{Delphes} a better resolution than in a real detector. Furthermore, muons leave no deposit in calorimeters. At last, the particles which might leak out of the calorimeters into the muon systems (\textit{punch-through}) will not be see409 n as muon candidates in \text sc{Delphes}.407 The application of the detector resolution on the muon momentum depends on a Gaussian smearing of the $p_T$ variable\footnote{\texttt{[code]} See the \texttt{SmearMuon} method.}. Neither $\eta$ nor $\phi$ variables are modified beyond the calorimeters: no additional magnetic field is applied. Multiple scattering is neglected. This implies that low energy muons have in \textit{Delphes} a better resolution than in a real detector. Furthermore, muons leave no deposit in calorimeters. At last, the particles which might leak out of the calorimeters into the muon systems (\textit{punch-through}) will not be see 408 n as muon candidates in \textit{Delphes}. 410 409 411 410 \subsubsection*{Charged lepton isolation} 412 411 \label{sec:isolation} 413 412 414 To improve the quality of the contents of the charged lepton collections, additional criteria can be applied such as isolation. This requires that electron or muon candidates are isolated in the detector from any other particle, within a small cone. In \text sc{Delphes}, charged lepton isolation demands that there is no other charged particle with $p_T>2~\textrm{GeV}/c$ within a cone of $\Delta R = \sqrt{\Delta \eta^2 + \Delta \phi^2} <0.5$ around the lepton.413 To improve the quality of the contents of the charged lepton collections, additional criteria can be applied such as isolation. This requires that electron or muon candidates are isolated in the detector from any other particle, within a small cone. In \textit{Delphes}, charged lepton isolation demands that there is no other charged particle with $p_T>2~\textrm{GeV}/c$ within a cone of $\Delta R = \sqrt{\Delta \eta^2 + \Delta \phi^2} <0.5$ around the lepton. 415 414 The result (i.e.\ \textit{isolated} or \textit{not}) is added to the charged lepton measured properties. 416 415 In addition, the sum $P_T$ of the transverse momenta of all tracks but the lepton one within the isolation cone is … … 425 424 \subsubsection*{Forward neutrals} 426 425 427 The zero degree calorimeter hits correspond to neutral particles with a lifetime long enough to reach these detectors (default: $c \tau \geq 140~\textrm{m}$) and very large pseudorapidities (default: $|\eta|>8.3$). In current versions of \text sc{Delphes}, only photons and neutrons are considered. Photons are identified thanks to the electromagnetic section of the calorimeter, and if their energy overpasses a given threshold (def. $20$~GeV). Similarly, neutrons are reconstructed according to the resolution of the hadronic section, if their energy exceeds a threshold\footnote{\texttt{[code]} These thresholds are defined by the \texttt{ZDC\_gamma\_E} and \texttt{ZDC\_n\_E} variables in the detector card.} (def. $50$~GeV).426 The zero degree calorimeter hits correspond to neutral particles with a lifetime long enough to reach these detectors (default: $c \tau \geq 140~\textrm{m}$) and very large pseudorapidities (default: $|\eta|>8.3$). In current versions of \textit{Delphes}, only photons and neutrons are considered. Photons are identified thanks to the electromagnetic section of the calorimeter, and if their energy overpasses a given threshold (def. $20$~GeV). Similarly, neutrons are reconstructed according to the resolution of the hadronic section, if their energy exceeds a threshold\footnote{\texttt{[code]} These thresholds are defined by the \texttt{ZDC\_gamma\_E} and \texttt{ZDC\_n\_E} variables in the detector card.} (def. $50$~GeV). 428 427 429 428 … … 431 430 \subsection{Jet reconstruction} 432 431 433 A realistic analysis requires a correct treatment of particles which have hadronised. Therefore, the most widely currently used jet algorithms have been integrated into the \text sc{Delphes} framework using the \textsc{FastJet} tools~\citep{bib:FastJet}.432 A realistic analysis requires a correct treatment of particles which have hadronised. Therefore, the most widely currently used jet algorithms have been integrated into the \textit{Delphes} framework using the FastJet tools~\citep{bib:FASTJET}. 434 433 Six different jet reconstruction schemes are available\footnote{\texttt{[code] }The choice is done by allocating the \texttt{JET\_jetalgo } input parameter in the detector card.}. The first three belong to the cone algorithm class while the last three are using a sequential recombination scheme. For all of them, the towers are used as input for the jet clustering. Jet algorithms differ in their sensitivity to soft particles or collinear splittings, and in their computing speed performances. 435 434 By default, reconstruction uses a cone algorithm with $\Delta R=0.7$. … … 441 440 442 441 \item {\it CDF Jet Clusters}~\citep{bib:jetclu}: Algorithm forming jets by associating together towers lying within a circle (default radius $\Delta R=0.7$) in the $(\eta$, $\phi)$ space. 443 This so-called \textsc{Jetclu} cone jet algorithm is used by the \textsc{cdf} experiment in Run II.442 This so-called JetCLU cone jet algorithm is used by the \textsc{CDF} experiment in Run II. 444 443 All towers with a transverse energy $E_T$ higher than a given threshold (default: $E_T > 1~\textrm{GeV}$) are used to seed the jet candidates. 445 The existing \textsc{FastJet} code has been modified to allow easy modification of the tower pattern in $(\eta, \phi)$ space.446 In following versions of \text sc{Delphes}, a new dedicated plug-in will be created on this purpose\footnote{\texttt{[code] }\texttt{JET\_coneradius} and \texttt{JET\_seed} variables in the detector card.}.447 448 \item {\it CDF MidPoint}~\citep{bib:midpoint}: Algorithm developed for the \textsc{ cdf} Run II to reduce infrared and collinear sensitivities compared to purely seed-based cone by adding `midpoints' (energy barycentres) in the list of cone seeds.449 450 \item {\it Seedless Infrared Safe Cone}~\citep{bib:SIScone}: The \textsc{SISC one}algorithm is simultaneously insensitive to additional soft particles and collinear splittings, and fast enough to be used in experimental analysis.444 The existing FastJet code has been modified to allow easy modification of the tower pattern in $(\eta, \phi)$ space. 445 In following versions of \textit{Delphes}, a new dedicated plug-in will be created on this purpose\footnote{\texttt{[code] }\texttt{JET\_coneradius} and \texttt{JET\_seed} variables in the detector card.}. 446 447 \item {\it CDF MidPoint}~\citep{bib:midpoint}: Algorithm developed for the \textsc{CDF} Run II to reduce infrared and collinear sensitivities compared to purely seed-based cone by adding `midpoints' (energy barycentres) in the list of cone seeds. 448 449 \item {\it Seedless Infrared Safe Cone}~\citep{bib:SIScone}: The \textsc{SISC}one algorithm is simultaneously insensitive to additional soft particles and collinear splittings, and fast enough to be used in experimental analysis. 451 450 452 451 \end{enumerate} … … 487 486 \subsubsection*{Energy flow} 488 487 489 In jets, several particle can leave their energy into a given calorimetric tower, which broadens the jet energy resolution. However, the energy of charged particles associated to jets can be deduced from their reconstructed track, thus providing a way to identify some of the components of towers with multiple hits. When the \textit{energy flow} is switched on in \text sc{Delphes}\footnote{\texttt{[code]} Set \texttt{JET\_Eflow} to $1$ or $0$ in the detector card in order to switch on or off the energy flow for jet reconstruction.}, the energy of tracks pointing to calotowers is extracted and smeared separately, before running the chosen jet reconstruction algorithm. This option allows a better jet $E$ reconstruction.488 In jets, several particle can leave their energy into a given calorimetric tower, which broadens the jet energy resolution. However, the energy of charged particles associated to jets can be deduced from their reconstructed track, thus providing a way to identify some of the components of towers with multiple hits. When the \textit{energy flow} is switched on in \textit{Delphes}\footnote{\texttt{[code]} Set \texttt{JET\_Eflow} to $1$ or $0$ in the detector card in order to switch on or off the energy flow for jet reconstruction.}, the energy of tracks pointing to calotowers is extracted and smeared separately, before running the chosen jet reconstruction algorithm. This option allows a better jet $E$ reconstruction. 490 489 491 490 \subsection{$b$-tagging} … … 493 492 494 493 A jet is tagged as $b$-jets if its direction lies in the acceptance of the tracker and if it is associated to a parent $b$-quark. By default, a $b$-tagging efficiency of $40\%$ is assumed if the jet has a parent $b$ quark. For $c$-jets and light jets (i.e.\ originating in $u$, $d$, $s$ quarks or in gluons), a fake $b$-tagging efficiency of $10 \%$ and $1 \%$ respectively is assumed\footnote{\texttt{[code] }Corresponding to the \texttt{BTAG\_b}, \texttt{BTAG\_mistag\_c} and \texttt{BTAG\_mistag\_l} constants, for (respectively) the efficiency of tagging of a $b$-jet, the efficiency of mistagging a $c$-jet as a $b$-jet, and the efficiency of mistagging a light jet ($u$,$d$,$s$,$g$) as a $b$-jet.}. 495 The (mis)tagging relies on the true particle identity (\textsc{ pid}) of the most energetic particle within a cone around the observed $(\eta,\phi)$ region, with a radius equal to the one used to reconstruct the jet (default: $\Delta R$ of $0.7$). In current version of \textsc{Delphes}, the displacement of secondary vertices is not simulated.494 The (mis)tagging relies on the true particle identity (\textsc{PID}) of the most energetic particle within a cone around the observed $(\eta,\phi)$ region, with a radius equal to the one used to reconstruct the jet (default: $\Delta R$ of $0.7$). In current version of \textit{Delphes}, the displacement of secondary vertices is not simulated. 496 495 497 496 \subsection{\texorpdfstring{$\tau$}{\texttau} identification} … … 564 563 \includegraphics[width=\columnwidth]{fig6} 565 564 \caption{Distribution of the electromagnetic collimation $C_\tau$ variable for true $\tau$-jets, normalised to unity. This distribution is shown for associated $WH$ photoproduction~\citep{bib:whphotoproduction}, where the Higgs boson decays into a $W^+ W^-$ pair. Each $W$ boson decays into a $\ell \nu_\ell$ pair, where $\ell = e, \mu, \tau$. 566 Events generated with \textsc{MadGraph/MadEvent}~\citep{bib:mgme}.567 Final state hadronisation is performed by \text sc{Pythia}~\citep{bib:pythia}.565 Events generated with MadGraph/MadEvent~\citep{bib:mgme}. 566 Final state hadronisation is performed by \textit{Pythia}~\citep{bib:pythia}. 568 567 Histogram entries correspond to true $\tau$-jets, matched with generator-level data. } 569 568 \label{fig:tau2} … … 610 609 \end{equation} 611 610 The \textit{true} missing transverse energy, i.e.\ at generator-level, is calculated as the opposite of the vector sum of the transverse momenta of all visible particles -- or equivalently, to the vector sum of invisible particle transverse momenta. 612 In a real experiment, calorimeters measure energy and not momentum. Any problem affecting the detector (dead channels, misalignment, noisy towers, cracks) worsens directly the measured missing transverse energy $\overrightarrow {E_T}^\textrm{miss}$. In this document, \textsc{ met} is based on the calorimetric towers and only muons and neutrinos are not taken into account for its evaluation\footnote{However, as tracks and calorimetric towers are available in the output file, the missing transverse energy can always be reprocessed a posteriori. }:611 In a real experiment, calorimeters measure energy and not momentum. Any problem affecting the detector (dead channels, misalignment, noisy towers, cracks) worsens directly the measured missing transverse energy $\overrightarrow {E_T}^\textrm{miss}$. In this document, \textsc{MET} is based on the calorimetric towers and only muons and neutrinos are not taken into account for its evaluation\footnote{However, as tracks and calorimetric towers are available in the output file, the missing transverse energy can always be reprocessed a posteriori. }: 613 612 \begin{equation} 614 613 \overrightarrow{E_T}^\textrm{miss} = - \sum^\textrm{towers}_i \overrightarrow{E_T}(i) … … 618 617 \section{Trigger emulation} 619 618 620 New physics in collider experiment are often characterised in phenomenology by low cross-section values, compared to the Standard Model (\textsc{ sm}) processes. %For instance at the \textsc{lhc} ($\sqrt{s}=14~\textrm{TeV}$), the cross-section of inclusive production of $b \bar b$ pairs is expected to be $10^7~\textrm{nb}$, or inclusive jets at $100~\textrm{nb}$ ($p_T > 200~\textrm{GeV}/c$), while Higgs boson cross-section within the \textsc{sm} can be as small as $2 \times 10^{-3}~\textrm{nb}$ ($pp \rightarrow WH$, $m_H=115~\textrm{GeV}/c^2$).619 New physics in collider experiment are often characterised in phenomenology by low cross-section values, compared to the Standard Model (\textsc{SM}) processes. %For instance at the \textsc{LHC} ($\sqrt{s}=14~\textrm{TeV}$), the cross-section of inclusive production of $b \bar b$ pairs is expected to be $10^7~\textrm{nb}$, or inclusive jets at $100~\textrm{nb}$ ($p_T > 200~\textrm{GeV}/c$), while Higgs boson cross-section within the \textsc{SM} can be as small as $2 \times 10^{-3}~\textrm{nb}$ ($pp \rightarrow WH$, $m_H=115~\textrm{GeV}/c^2$). 621 620 622 621 %High statistics are required for data analyses, consequently imposing high luminosity, i.e.\ a high collision rate. 623 622 As only a tiny fraction of the observed events can be stored for subsequent \textit{offline} analyses, a very large data rejection factor should be applied directly as the events are produced. 624 This data selection is supposed to reject only well-known \textsc{ sm} events\footnote{However, some bandwidth is allocated to minimum-bias and/or zero-bias (``random'') triggers that stores a small fraction of the events without any selection criteria.}.623 This data selection is supposed to reject only well-known \textsc{SM} events\footnote{However, some bandwidth is allocated to minimum-bias and/or zero-bias (``random'') triggers that stores a small fraction of the events without any selection criteria.}. 625 624 Dedicated algorithms of this \textit{online} selection, or \textit{trigger}, should be fast and very efficient for data rejection, in order to preserve the experiment output bandwidth. They must also be as inclusive as possible to avoid loosing interesting events. 626 625 627 Most of the usual trigger algorithms select events containing objects (i.e.\ jets, particles, \textsc{ met}) with an energy scale above some threshold. This is often expressed in terms of a cut on the transverse momentum of one or several objects of the measured event. Logical combinations of several conditions are also possible. For instance, a trigger path could select events containing at least one jet and one electron such as $p_T^\textrm{jet} > 100~\textrm{GeV}/c$ and $p_T^e > 50~\textrm{GeV}/c$.628 629 A trigger emulation is included in \text sc{Delphes}, using a fully parametrisable \textit{trigger table}\footnote{\texttt{[code] }The trigger card is the \texttt{data/TriggerCard.dat} file.}. When enabled, this trigger is applied on analysis-object data.626 Most of the usual trigger algorithms select events containing objects (i.e.\ jets, particles, \textsc{MET}) with an energy scale above some threshold. This is often expressed in terms of a cut on the transverse momentum of one or several objects of the measured event. Logical combinations of several conditions are also possible. For instance, a trigger path could select events containing at least one jet and one electron such as $p_T^\textrm{jet} > 100~\textrm{GeV}/c$ and $p_T^e > 50~\textrm{GeV}/c$. 627 628 A trigger emulation is included in \textit{Delphes}, using a fully parametrisable \textit{trigger table}\footnote{\texttt{[code] }The trigger card is the \texttt{data/TriggerCard.dat} file.}. When enabled, this trigger is applied on analysis-object data. 630 629 In a real experiment, the online selection is often divided into several steps (or \textit{levels}). 631 630 This splits the overall reduction factor into a product of smaller factors, corresponding to the different trigger levels. … … 635 634 636 635 Real triggers are thus intrinsically based on reconstructed data with a worse resolution than final analysis data. 637 On the contrary, same data are used in \text sc{Delphes} for trigger emulation and for final analyses.636 On the contrary, same data are used in \textit{Delphes} for trigger emulation and for final analyses. 638 637 639 638 \section{Validation} 640 639 641 \text sc{Delphes} performs a fast simulation of a collider experiment.640 \textit{Delphes} performs a fast simulation of a collider experiment. 642 641 Its performances in terms of computing time and data size are directly proportional to the number of simulated events and on the considered physics process. As an example, $10,000$ $pp \rightarrow t \bar t X$ events are processed in $110~\textrm{s}$ on a regular laptop and use less than $250~\textrm{MB}$ of disk space. 643 The quality and validity of the output are assessed by comparing the resolutions on the reconstructed data to the expectations of both \textsc{ cms}~\citep{bib:cmsjetresolution} and \textsc{atlas}~\citep{bib:ATLASresolution} detectors.642 The quality and validity of the output are assessed by comparing the resolutions on the reconstructed data to the expectations of both \textsc{CMS}~\citep{bib:cmsjetresolution} and \textsc{ATLAS}~\citep{bib:ATLASresolution} detectors. 644 643 645 644 Electrons and muons are by construction equal to the experiment designs, as the Gaussian smearing of their kinematics properties is defined according to the detector specifications. … … 649 648 \subsection{Jet resolution} 650 649 651 The majority of interesting processes at the \textsc{ lhc} contain jets in the final state. The jet resolution obtained using \textsc{Delphes} is therefore a crucial point for its validation, both for \textsc{cms}- and \textsc{atlas}-like detectors.652 This validation is based on $pp \rightarrow gg$ events produced with \textsc{MadGraph/MadEvent} and hadronised using \textsc{Pythia}~\citep{bib:mgme,bib:pythia}.653 654 For a \textsc{ cms}-like detector, a similar procedure as the one explained in published results is applied here.655 The events were arranged in $14$ bins of gluon transverse momentum $\hat{p}_T$. In each $\hat{p}_T$ bin, every jet in \text sc{Delphes} is matched to the closest jet of generator-level particles, using the spatial separation between the two jet axes650 The majority of interesting processes at the \textsc{LHC} contain jets in the final state. The jet resolution obtained using \textit{Delphes} is therefore a crucial point for its validation, both for \textsc{CMS}- and \textsc{ATLAS}-like detectors. 651 This validation is based on $pp \rightarrow gg$ events produced with MadGraph/MadEvent and hadronised using \textit{Pythia}~\citep{bib:mgme,bib:pythia}. 652 653 For a \textsc{CMS}-like detector, a similar procedure as the one explained in published results is applied here. 654 The events were arranged in $14$ bins of gluon transverse momentum $\hat{p}_T$. In each $\hat{p}_T$ bin, every jet in \textit{Delphes} is matched to the closest jet of generator-level particles, using the spatial separation between the two jet axes 656 655 \begin{equation} 657 656 \Delta R = \sqrt{ \big(\eta^\textrm{rec} - \eta^\textrm{MC} \big)^2 + \big(\phi^\textrm{rec} - \phi^\textrm{MC} \big)^2}<0.25. 658 657 \end{equation} 659 658 The jets made of generator-level particles, here referred as \textit{MC jets}, are obtained by applying the algorithm to all particles considered as stable after hadronisation (i.e.\ including muons). 660 Jets produced by \text sc{Delphes} and satisfying the matching criterion are called hereafter \textit{reconstructed jets}.661 All jets are computed with the clustering algorithm ( \textsc{jetclu}) with a cone radius $R$ of $0.7$.662 663 The ratio of the transverse energies of every reconstructed jet $E_T^\textrm{rec}$ to its corresponding \textsc{ mc} jet $E_T^\textrm{MC}$ is calculated in each $\hat{p}_T$ bin.664 The $E_T^\textrm{rec}/E_T^\textrm{MC}$ histogram is fitted with a Gaussian distribution in the interval \mbox{$\pm 2$~\textsc{ rms}} centred around the mean value.659 Jets produced by \textit{Delphes} and satisfying the matching criterion are called hereafter \textit{reconstructed jets}. 660 All jets are computed with the clustering algorithm (JetCLU) with a cone radius $R$ of $0.7$. 661 662 The ratio of the transverse energies of every reconstructed jet $E_T^\textrm{rec}$ to its corresponding \textsc{MC} jet $E_T^\textrm{MC}$ is calculated in each $\hat{p}_T$ bin. 663 The $E_T^\textrm{rec}/E_T^\textrm{MC}$ histogram is fitted with a Gaussian distribution in the interval \mbox{$\pm 2$~\textsc{RMS}} centred around the mean value. 665 664 The resolution in each $\hat{p}_T$ bin is obtained by the fit mean $\langle x \rangle$ and variance $\sigma^2(x)$: 666 665 \begin{equation} … … 674 673 %\includegraphics[width=\columnwidth]{resolutionJet} 675 674 \includegraphics[width=\columnwidth]{fig8} 676 \caption{Resolution of the transverse energy of reconstructed jets $E_T^\textrm{rec}$ as a function of the transverse energy of the closest jet of generator-level particles $E_T^\textrm{MC}$, in a \textsc{ cms}-like detector. The jets events are reconstructed with the \textsc{jetclu} clustering algorithm with a cone radius of $0.7$. The maximum separation between the reconstructed and \textsc{mc}-jets is $\Delta R= 0.25$. Dotted line is the fit result for comparison to the \textsc{cms} resolution~\citep{bib:cmsjetresolution}, in blue. The $pp \rightarrow gg$ dijet events have been generated with \textsc{MadGraph/MadEvent} and hadronised with \textsc{Pythia}.}675 \caption{Resolution of the transverse energy of reconstructed jets $E_T^\textrm{rec}$ as a function of the transverse energy of the closest jet of generator-level particles $E_T^\textrm{MC}$, in a \textsc{CMS}-like detector. The jets events are reconstructed with the JetCLU clustering algorithm with a cone radius of $0.7$. The maximum separation between the reconstructed and \textsc{MC}-jets is $\Delta R= 0.25$. Dotted line is the fit result for comparison to the \textsc{CMS} resolution~\citep{bib:cmsjetresolution}, in blue. The $pp \rightarrow gg$ dijet events have been generated with MadGraph/MadEvent and hadronised with \textit{Pythia}.} 677 676 \label{fig:jetresolcms} 678 677 \end{center} … … 686 685 \end{equation} 687 686 where $a$, $b$ and $c$ are the fit parameters. 688 It is then compared to the resolution published by the \textsc{ cms} collaboration~\citep{bib:cmsjetresolution}. The resolution curves from \textsc{Delphes} and \textsc{cms} are in good agreement.689 690 Similarly, the jet resolution is evaluated for an \textsc{ atlas}-like detector. The $pp \rightarrow gg$ events are here arranged in $8$ adjacent bins in $p_T$. A $k_T$ reconstruction algorithm with $R=0.6$ is chosen and the maximal matching distance between the \textsc{mc}-jets and the reconstructed jets is set to $\Delta R=0.2$. The relative energy resolution is evaluated in each bin by:687 It is then compared to the resolution published by the \textsc{CMS} collaboration~\citep{bib:cmsjetresolution}. The resolution curves from \textit{Delphes} and \textsc{CMS} are in good agreement. 688 689 Similarly, the jet resolution is evaluated for an \textsc{ATLAS}-like detector. The $pp \rightarrow gg$ events are here arranged in $8$ adjacent bins in $p_T$. A $k_T$ reconstruction algorithm with $R=0.6$ is chosen and the maximal matching distance between the \textsc{MC}-jets and the reconstructed jets is set to $\Delta R=0.2$. The relative energy resolution is evaluated in each bin by: 691 690 \begin{equation} 692 691 \frac{\sigma(E)}{E} = \sqrt{~~ \Bigg \langle ~\Bigg( \frac{E^\textrm{rec} - E^\textrm{MC}}{E^\textrm{rec}} \Bigg)^2 ~ \Bigg \rangle ~ - ~ \Bigg \langle \frac{E^\textrm{rec} - E^\textrm{MC}}{ E^\textrm{rec} } \Bigg \rangle^2}. 693 692 \end{equation} 694 693 695 Figure~\ref{fig:jetresolatlas} shows a good agreement between the resolution obtained with \text sc{Delphes}, the result of the fit with Equation~\ref{eq:fitresolution} and the corresponding curve provided by the \textsc{atlas} collaboration~\citep{bib:ATLASresolution}.694 Figure~\ref{fig:jetresolatlas} shows a good agreement between the resolution obtained with \textit{Delphes}, the result of the fit with Equation~\ref{eq:fitresolution} and the corresponding curve provided by the \textsc{ATLAS} collaboration~\citep{bib:ATLASresolution}. 696 695 697 696 \begin{figure}[!ht] 698 697 \begin{center} 699 698 \includegraphics[width=\columnwidth]{fig9} 700 \caption{Relative energy resolution of reconstructed jets as a function of the energy of the closest jet of generator-level particles $E^\textrm{MC}$, in an \textsc{ atlas}-like detector. The jets are reconstructed with the $k_T$ algorithm with a radius $R=0.6$. The maximal matching distance between \textsc{mc}- and reconstructed jets is $\Delta R=0.2$. Only central jets are considered ($|\eta|<0.5$). Dotted line is the fit result for comparison to the \textsc{atlas} resolution~\citep{bib:ATLASresolution}, in blue. The $pp \rightarrow gg$ di-jet events have been generated with \textsc{MadGraph/MadEvent} and hadronised with \textsc{Pythia}.}699 \caption{Relative energy resolution of reconstructed jets as a function of the energy of the closest jet of generator-level particles $E^\textrm{MC}$, in an \textsc{ATLAS}-like detector. The jets are reconstructed with the $k_T$ algorithm with a radius $R=0.6$. The maximal matching distance between \textsc{MC}- and reconstructed jets is $\Delta R=0.2$. Only central jets are considered ($|\eta|<0.5$). Dotted line is the fit result for comparison to the \textsc{ATLAS} resolution~\citep{bib:ATLASresolution}, in blue. The $pp \rightarrow gg$ di-jet events have been generated with MadGraph/MadEvent and hadronised with \textit{Pythia}.} 701 700 \label{fig:jetresolatlas} 702 701 \end{center} … … 707 706 708 707 All major detectors at hadron colliders have been designed to be as much hermetic as possible in order to detect the presence of one or more neutrinos and/or new weakly interacting particles through apparent missing transverse energy. 709 The resolution of the $\overrightarrow{E_T}^\textrm{miss}$ variable, as obtained with \text sc{Delphes}, is then crucial.710 711 The samples used to study the \textsc{ met} performance are identical to those used for the jet validation.708 The resolution of the $\overrightarrow{E_T}^\textrm{miss}$ variable, as obtained with \textit{Delphes}, is then crucial. 709 710 The samples used to study the \textsc{MET} performance are identical to those used for the jet validation. 712 711 It is worth noting that the contribution to $E_T^\textrm{miss}$ from muons is negligible in the studied sample. 713 712 The input samples are divided in five bins of scalar $E_T$ sums $(\Sigma E_T)$. This sum, called \textit{total visible transverse energy}, is defined as the scalar sum of transverse energy in all towers. 714 The quality of the \textsc{ met} reconstruction is checked via the resolution on its horizontal component $E_x^\textrm{miss}$.713 The quality of the \textsc{MET} reconstruction is checked via the resolution on its horizontal component $E_x^\textrm{miss}$. 715 714 716 715 The $E_x^\textrm{miss}$ resolution is evaluated in the following way. 717 The distribution of the difference between $E_x^\textrm{miss}$ in \text sc{Delphes} and at generator-level is fitted with a Gaussian function in each $(\Sigma E_T)$ bin. The fit \textsc{rms} gives the \textsc{met} resolution in each bin.716 The distribution of the difference between $E_x^\textrm{miss}$ in \textit{Delphes} and at generator-level is fitted with a Gaussian function in each $(\Sigma E_T)$ bin. The fit \textsc{RMS} gives the \textsc{MET} resolution in each bin. 718 717 The resulting value is plotted in Fig.~\ref{fig:resolETmis} as a function of the total visible transverse 719 energy, for \textsc{ cms}- and \textsc{atlas}-like detectors.718 energy, for \textsc{CMS}- and \textsc{ATLAS}-like detectors. 720 719 721 720 \begin{figure}[!ht] … … 724 723 \includegraphics[width=\columnwidth]{fig10} 725 724 \includegraphics[width=\columnwidth]{fig10b} 726 \caption{$\sigma(E^\textrm{mis}_{x})$ as a function on the scalar sum of all towers ($\Sigma E_T$) for $pp \rightarrow gg$ events, for a \textsc{ cms}-like detector (top) and an \textsc{atlas}-like detector (bottom), for di-jet events produced with \textsc{MadGraph/MadEvent} and hadronised with \textsc{Pythia}.}725 \caption{$\sigma(E^\textrm{mis}_{x})$ as a function on the scalar sum of all towers ($\Sigma E_T$) for $pp \rightarrow gg$ events, for a \textsc{CMS}-like detector (top) and an \textsc{ATLAS}-like detector (bottom), for di-jet events produced with MadGraph/MadEvent and hadronised with \textit{Pythia}.} 727 726 \label{fig:resolETmis} 728 727 \end{center} 729 728 \end{figure} 730 729 731 The resolution $\sigma_x$ of the horizontal component of \textsc{ met} is observed to behave like730 The resolution $\sigma_x$ of the horizontal component of \textsc{MET} is observed to behave like 732 731 \begin{equation} 733 732 \sigma_x = \alpha ~\sqrt{E_T}~~~(\mathrm{GeV}^{1/2}), … … 735 734 where the $\alpha$ parameter depends on the resolution of the calorimeters. 736 735 737 The \textsc{ met} resolution expected for the \textsc{cms} detector for similar events is $\sigma_x = (0.6-0.7) ~ \sqrt{E_T} ~ \mathrm{GeV}^{1/2}$ with no pile-up\footnote{\textit{Pile-up} events are extra simultaneous $pp$ collision occurring at high-luminosity in the same bunch crossing.}~\citep{bib:cmsjetresolution}, which compares very well with the $\alpha = 0.63$ obtained with \textsc{Delphes}. Similarly, for an \textsc{atlas}-like detector, a value of $0.53$ is obtained by \textsc{Delphes} for the $\alpha$ parameter, while the experiment expects it in the range $[0.53~ ;~0.57]$~\citep{bib:ATLASresolution}.736 The \textsc{MET} resolution expected for the \textsc{CMS} detector for similar events is $\sigma_x = (0.6-0.7) ~ \sqrt{E_T} ~ \mathrm{GeV}^{1/2}$ with no pile-up\footnote{\textit{Pile-up} events are extra simultaneous $pp$ collision occurring at high-luminosity in the same bunch crossing.}~\citep{bib:cmsjetresolution}, which compares very well with the $\alpha = 0.63$ obtained with \textit{Delphes}. Similarly, for an \textsc{ATLAS}-like detector, a value of $0.53$ is obtained by \textit{Delphes} for the $\alpha$ parameter, while the experiment expects it in the range $[0.53~ ;~0.57]$~\citep{bib:ATLASresolution}. 738 737 739 738 \subsection{\texorpdfstring{$\tau$}{\texttau}-jet efficiency} 740 739 Due to the complexity of their reconstruction algorithm, $\tau$-jets have also to be checked. 741 Table~\ref{tab:taurecoefficiency} lists the reconstruction efficiencies in \text sc{Delphes} for the hadronic $\tau$-jets from $H,Z \rightarrow \tau^+ \tau^-$. The mass of the Higgs boson is set successively to $140$ and $300~\textrm{GeV}/c^2$. The inclusive gauge boson productions ($pp \rightarrow HX$ and $pp \rightarrow ZX$) are performed with \textsc{MadGraph/MadEvent} and the $\tau$ lepton decay and further hadronisation are handled by \textsc{Pythia/Tauola}. All reconstructed $\tau$-jets are $1-$prong, and follow the definition described in section~\ref{btagging}, which is very close to an algorithm of the \textsc{cms} experiment~\citep{bib:cmstauresolution}. At last, corresponding efficiencies published by the \textsc{cms} and \textsc{atlas} experiments are quoted for comparison. The agreement is good enough at this level to validate the $\tau-$reconstruction.740 Table~\ref{tab:taurecoefficiency} lists the reconstruction efficiencies in \textit{Delphes} for the hadronic $\tau$-jets from $H,Z \rightarrow \tau^+ \tau^-$. The mass of the Higgs boson is set successively to $140$ and $300~\textrm{GeV}/c^2$. The inclusive gauge boson productions ($pp \rightarrow HX$ and $pp \rightarrow ZX$) are performed with MadGraph/MadEvent and the $\tau$ lepton decay and further hadronisation are handled by \textit{Pythia/Tauola}. All reconstructed $\tau$-jets are $1-$prong, and follow the definition described in section~\ref{btagging}, which is very close to an algorithm of the \textsc{CMS} experiment~\citep{bib:cmstauresolution}. At last, corresponding efficiencies published by the \textsc{CMS} and \textsc{ATLAS} experiments are quoted for comparison. The agreement is good enough at this level to validate the $\tau-$reconstruction. 742 741 743 742 \begin{table}[!h] 744 743 \begin{center} 745 \caption{Reconstruction efficiencies of $\tau$-jets in $\tau^+ \tau^-$ decays from $Z$ or $H$ bosons, in \text sc{Delphes}, \textsc{cms} and \textsc{atlas} experiments~\citep{bib:cmstauresolution,bib:ATLASresolution}. Two scenarios for the mass of the Higgs boson are investigated. Events generated with \textsc{MadGraph/MadEvent} and hadronised with \textsc{Pythia}. The decays of $\tau$ leptons is handled by the \textsc{Tauola} version embedded in \textsc{Pythia}.\vspace{0.5cm}}744 \caption{Reconstruction efficiencies of $\tau$-jets in $\tau^+ \tau^-$ decays from $Z$ or $H$ bosons, in \textit{Delphes}, \textsc{CMS} and \textsc{ATLAS} experiments~\citep{bib:cmstauresolution,bib:ATLASresolution}. Two scenarios for the mass of the Higgs boson are investigated. Events generated with MadGraph/MadEvent and hadronised with \textit{Pythia}. The decays of $\tau$ leptons is handled by the \textit{Tauola} version embedded in \textit{Pythia}.\vspace{0.5cm}} 746 745 %\begin{tabular}{lll} 747 746 %\hline 748 %\multicolumn{2}{c}{\textsc{ cms}} & \\747 %\multicolumn{2}{c}{\textsc{CMS}} & \\ 749 748 %$Z \rightarrow \tau^+ \tau^-$ & $38 \%$ & \\ 750 749 %$H \rightarrow \tau^+ \tau^-$ & $36 \%$ & $m_H = 150~\textrm{GeV}/c^2$ \\ 751 750 %$H \rightarrow \tau^+ \tau^-$ & $47 \%$ & $m_H = 300~\textrm{GeV}/c^2$ \\ 752 %\multicolumn{2}{c}{ \textsc{Delphes}} & \\751 %\multicolumn{2}{c}{Delphes} & \\ 753 752 %$H \rightarrow \tau^+ \tau^-$ &$42 \%$ & $m_H = 140~\textrm{GeV}/c^2$ \\ 754 753 %\hline … … 757 756 \begin{tabular}{lrlrl} 758 757 \hline 759 & \textsc{ cms}&\textsc{Delphes} & \textsc{atlas}&\textsc{Delphes}\\758 & \textsc{CMS}&Delphes & \textsc{ATLAS}&Delphes \\ 760 759 $Z \rightarrow \tau^+ \tau^-$ & $38.2\%$ & $32.4\pm1.8\%$ & $33\%$ & $28.6\pm 1.9\%$ \\ 761 760 $H(140) \rightarrow \tau^+ \tau^-$ & $36.3\%$ & $39.9\pm1.6\%$ & & $32.8\pm 1.8\%$ \\ … … 771 770 \section{Visualisation} 772 771 773 When performing an event analysis, a visualisation tool is useful to convey information about the detector layout and the event topology in a simple way. The \textit{Fast and Realistic OpenGL Displayer} \textsc{ frog}~\citep{bib:Frog} has been interfaced in \textsc{Delphes}, allowing an easy display of the defined detector configuration\footnote{\texttt{[code] } To prepare the visualisation, the \texttt{FLAG\_frog} parameter should be equal to $1$.}.772 When performing an event analysis, a visualisation tool is useful to convey information about the detector layout and the event topology in a simple way. The \textit{Fast and Realistic OpenGL Displayer} \textsc{FROG}~\citep{bib:FROG} has been interfaced in \textit{Delphes}, allowing an easy display of the defined detector configuration\footnote{\texttt{[code] } To prepare the visualisation, the \texttt{FLAG\_FROG} parameter should be equal to $1$.}. 774 773 775 774 % \begin{figure}[!ht] 776 775 % \begin{center} 777 % \includegraphics[width=\columnwidth]{Detector_D elphes_1}778 % \caption{Layout of the generic detector geometry assumed in \textsc{Delphes}. The innermost layer, close to the interaction point, is a central tracking system (pink), embedded into a solenoidal magnetic field.776 % \includegraphics[width=\columnwidth]{Detector_DELPHES_1} 777 % \caption{Layout of the generic detector geometry assumed in Delphes. The innermost layer, close to the interaction point, is a central tracking system (pink), embedded into a solenoidal magnetic field. 779 778 % It is surrounded by a central calorimeter volume (green) with both electromagnetic and hadronic sections. 780 779 % The outer layer of the central system (red) consist of a muon system. … … 796 795 \begin{figure}[!ht] 797 796 \begin{center} 798 %\includegraphics[width=\columnwidth]{Detector_D elphes_2b}797 %\includegraphics[width=\columnwidth]{Detector_DELPHES_2b} 799 798 \includegraphics[width=\columnwidth]{fig11} 800 \caption{Layout of the generic detector geometry assumed in \text sc{Delphes}. Open 3D-view of the detector with solid volumes. Same colour codes as for Fig.~\ref{fig:GenDet3} are applied. Additional forward detectors are not depicted.}799 \caption{Layout of the generic detector geometry assumed in \textit{Delphes}. Open 3D-view of the detector with solid volumes. Same colour codes as for Fig.~\ref{fig:GenDet3} are applied. Additional forward detectors are not depicted.} 801 800 \label{fig:GenDet2} 802 801 \end{center} … … 817 816 \begin{figure}[!ht] 818 817 \begin{center} 819 %%\includegraphics[width=\columnwidth]{Events_D elphes_1}818 %%\includegraphics[width=\columnwidth]{Events_DELPHES_1} 820 819 %\includegraphics[width=\columnwidth]{DisplayWt} 821 820 \includegraphics[width=\columnwidth]{fig12} … … 834 833 \begin{figure}[!ht] 835 834 \begin{center} 836 %%\includegraphics[width=\columnwidth]{Events_D elphes_1}835 %%\includegraphics[width=\columnwidth]{Events_DELPHES_1} 837 836 %\includegraphics[width=\columnwidth]{Displayppgg} 838 837 \includegraphics[width=\columnwidth]{fig13} … … 846 845 847 846 % \subsection{version 1} 848 % We have described here the major features of the \text sc{Delphes} framework, introduced for the fast simulation of a collider experiment.849 % It has already been used for several phenomenological studies, in particular in photon interactions at the \textsc{ lhc}.847 % We have described here the major features of the \textit{Delphes} framework, introduced for the fast simulation of a collider experiment. 848 % It has already been used for several phenomenological studies, in particular in photon interactions at the \textsc{LHC}. 850 849 % 851 % \text sc{Delphes} takes the output of event generators, in various formats, and yields analysis-object data.850 % \textit{Delphes} takes the output of event generators, in various formats, and yields analysis-object data. 852 851 % The simulation applies the resolutions of central and forward detectors by smearing the kinematical properties of final state particles. 853 852 % It yields tracks in a solenoidal magnetic field and calorimetric towers. 854 % Realistic reconstruction algorithms are run, including the \textsc{FastJet} package, to produce collections of $e^\pm$, $\mu^\pm$, jets and $\tau$-jets. $b$-tag and missing transverse energy are also evaluated.855 % The output is validated by comparing to the \textsc{ cms} expected performances.853 % Realistic reconstruction algorithms are run, including the FastJet package, to produce collections of $e^\pm$, $\mu^\pm$, jets and $\tau$-jets. $b$-tag and missing transverse energy are also evaluated. 854 % The output is validated by comparing to the \textsc{CMS} expected performances. 856 855 % A trigger stage can be emulated on the output data. 857 % At last, event visualisation is possible through the \textsc{F rog} 3D event display.856 % At last, event visualisation is possible through the \textsc{FROG} 3D event display. 858 857 % 859 858 % 860 % \text sc{Delphes} has been developped using the parameters of the \textsc{cms} experiment but can be easily extended to \textsc{atlas} and other non-\textsc{lhc} experiments, as at Tevatron or at the \textsc{ilc}. Further developments include a more flexible design for the subdetector assembly and possibly the implementation of an event mixing module for pile-up event simulation.859 % \textit{Delphes} has been developped using the parameters of the \textsc{CMS} experiment but can be easily extended to \textsc{ATLAS} and other non-\textsc{LHC} experiments, as at Tevatron or at the \textsc{ILC}. Further developments include a more flexible design for the subdetector assembly and possibly the implementation of an event mixing module for pile-up event simulation. 861 860 % 862 861 % 863 862 % \subsection{version 2} 864 We have described here the major features of the \text sc{Delphes} framework, introduced for the fast simulation of a collider experiment. This framework is a tool meant for feasibility studies in phenomenology, gauging the observability of model predictions in collider experiments.865 866 \text sc{Delphes} takes as an input the output of event-generators and yields analysis-object data in the form of \texttt{TTree} in a \textsc{root} file.863 We have described here the major features of the \textit{Delphes} framework, introduced for the fast simulation of a collider experiment. This framework is a tool meant for feasibility studies in phenomenology, gauging the observability of model predictions in collider experiments. 864 865 \textit{Delphes} takes as an input the output of event-generators and yields analysis-object data in the form of \texttt{TTree} in a \texttt{*.root} file. 867 866 The simulation includes central and forward detectors to produce realistic observables using standard reconstruction algorithms. 868 867 Moreover, the framework allows trigger emulation and 3D event visualisation. 869 868 870 \text sc{Delphes} has been developed using the parameters of the \textsc{cms} experiment but can be easily extended to \textsc{atlas} and other non-\textsc{lhc} experiments, as at Tevatron or at the \textsc{ilc}. Further developments include a more flexible design for the subdetector assembly and possibly the implementation of an event mixing module for pile-up event simulation.871 872 This framework has already been used for several analyses, in particular in photon-induced interactions at the \textsc{ lhc}~\citep{bib:wtphotoproduction, bib:papierquisortirajamais, bib:papiersimon}.869 \textit{Delphes} has been developed using the parameters of the \textsc{CMS} experiment but can be easily extended to \textsc{ATLAS} and other non-\textsc{LHC} experiments, as at Tevatron or at the \textsc{ILC}. Further developments include a more flexible design for the subdetector assembly and possibly the implementation of an event mixing module for pile-up event simulation. 870 871 This framework has already been used for several analyses, in particular in photon-induced interactions at the \textsc{LHC}~\citep{bib:wtphotoproduction, bib:papierquisortirajamais, bib:papiersimon}. 873 872 874 873 875 874 \section*{Acknowledgements} 876 875 \addcontentsline{toc}{section}{Acknowledgements} 877 The authors would like to thank very warmly Vincent Lema\^itre for the interesting suggestions during the development of the software, as well as Jer\^ome de Favereau, Christophe Delaere, Muriel Vander Donckt and David d'Enterria for useful discussions and comments, and Loic Quertenmont for support in interfacing \textsc{Frog}. We are also really grateful to Alice Dechambre and Simon de Visscher for being beta testers of the complete package.876 The authors would like to thank Jer\^ome de Favereau, Christophe Delaere, Muriel Vander Donckt and David d'Enterria for useful discussions and comments, and Loic Quertenmont for support in interfacing \textsc{FROG}. We are also really grateful to Alice Dechambre and Simon de Visscher for being beta testers of the complete package. 878 877 Part of this work was supported by the Belgian Federal Office for Scientific, Technical and Cultural Affairs through the Interuniversity Attraction Pole P6/11. 879 878 … … 882 881 \addcontentsline{toc}{section}{References} 883 882 884 \bibitem{bib: Delphes} \textsc{Delphes}, \href{http://www.fynu.ucl.ac.be/delphes.html}{www.fynu.ucl.ac.be/delphes.html}883 \bibitem{bib:delphes} \textit{Delphes}, \href{http://www.fynu.ucl.ac.be/delphes.html}{www.fynu.ucl.ac.be/delphes.html} 885 884 %hepforge: 886 885 \bibitem{bib:stdhep} L.A. Garren, M. Fischler, \href{http://cepa.fnal.gov/psm/stdhep/c++}{cepa.fnal.gov/psm/stdhep/c++} 887 886 \bibitem{bib:hepmc} M. Dobbs and J.B. Hansen, \textbf{Comput. Phys. Commun.} \href{http://dx.doi.org/10.1016/S0010-4655(00)00189-2}{134 (2001) 41}. 888 887 \bibitem{bib:lhe} J. Alwall, et al., \textbf{Comput. Phys. Commun.} \href{http://dx.doi.org/10.1016/j.cpc.2006.11.010}{176:300-304,2007}. 889 \bibitem{bib:Root} %\textsc{R oot}, \textit{An Object Oriented Data Analysis Framework},888 \bibitem{bib:Root} %\textsc{ROOT}, \textit{An Object Oriented Data Analysis Framework}, 890 889 R. Brun, F. Rademakers, Nucl. Inst. \& Meth. in \textbf{Phys. Res. A} \href{http://dx.doi.org/10.1016/S0168-9002(97)00048-X}{389 (1997) 81-86}. 891 890 \bibitem{bib:ExRootAnalysis} %\textit{The} \textsc{ExRootAnalysis} \textit{analysis steering utility}, 892 P. Demin, (2006), unpublished. Now part of \textsc{MadGraph/MadEvent}.893 \bibitem{bib:cmsjetresolution} The \textsc{ cms} Collaboration, \textbf{CERN/LHCC} \href{http://documents.cern.ch/cgi-bin/setlink?base=lhcc&categ=public&id=lhcc-2006-001}{2006-001}.894 \bibitem{bib:ATLASresolution} The \textsc{ atlas} Collaboration, \textbf{CERN-OPEN} 2008-020, \\arXiv:\href{http://arxiv.org/abs/arxiv:0901.0512}{0901.0512v1}[hep-ex].895 \bibitem{bib: Hector} %\textsc{Hector}, \textit{a fast simulator for the transport of particles in beamlines},891 P. Demin, (2006), unpublished. Now part of MadGraph/MadEvent. 892 \bibitem{bib:cmsjetresolution} The \textsc{CMS} Collaboration, \textbf{CERN/LHCC} \href{http://documents.cern.ch/cgi-bin/setlink?base=LHCc&categ=public&id=LHCc-2006-001}{2006-001}. 893 \bibitem{bib:ATLASresolution} The \textsc{ATLAS} Collaboration, \textbf{CERN-OPEN} 2008-020, \\arXiv:\href{http://arxiv.org/abs/arxiv:0901.0512}{0901.0512v1}[hep-ex]. 894 \bibitem{bib:hector} %\textit{Hector}, \textit{a fast simulator for the transport of particles in beamlines}, 896 895 X. Rouby, J. de Favereau, K. Piotrzkowski, \textbf{JINST} \href{http://www.iop.org/EJ/abstract/1748-0221/2/09/P09005}{2 P09005 (2007)}. 897 \bibitem{bib:F astJet} %\textit{The} \textsc{FastJet} \textit{package},896 \bibitem{bib:FASTJET} %\textit{The} FastJet \textit{package}, 898 897 M. Cacciari, G.P. Salam, \textbf{Phys. Lett. B} \href{http://dx.doi.org/10.1016/j.physletb.2006.08.037}{641 (2006) 57}. 899 \bibitem{bib:jetclu} %\textsc{ cdf} Run I legacy algorithm,898 \bibitem{bib:jetclu} %\textsc{CDF} Run I legacy algorithm, 900 899 F. Abe et al. (CDF Coll.), \textbf{Phys. Rev. D} \href{http://link.aps.org/doi/10.1103/PhysRevD.45.1448}{45 (1992) 1448}. 901 900 \bibitem{bib:midpoint} %Run II Jet Physics: Proceedings of the Run II QCD and Weak Boson Physics Workshop, 902 901 G.C. Blazey, et al., arXiv:\href{http://arxiv.org/abs/hep-ex/0005012}{0005012}[hep-ex]. 903 \bibitem{bib:SIScone} %\textsc{SIS cone}, \textit{A practical Seedless Infrared-Safe Cone jet algorithm},902 \bibitem{bib:SIScone} %\textsc{SISC}one, \textit{A practical Seedless Infrared-Safe Cone jet algorithm}, 904 903 G.P. Salam, G. Soyez, \textbf{JHEP} \href{http://dx.doi.org/10.1088/1126-6708/2007/05/086}{05 (2007) 086}. 905 904 \bibitem{bib:ktjet} S. Catani, Y.L. Dokshitzer, M.H. Seymour, B.R. Webber, \textbf{Nucl. Phys. B} \href{http://dx.doi.org/10.1016/0550-3213(93)90166-M}{406 (1993) 187}; S.D. Ellis, D.E. Soper, \textbf{Phys. Rev. D} \href{http://link.aps.org/doi/10.1103/PhysRevD.48.3160}{48 (1993) 3160}. … … 915 914 \bibitem{bib:cmstauresolution} %\textit{Study of $\tau$-jet identification in CMS}, 916 915 R. Kinnunen, A.N. Nikitenko, \textbf{CMS NOTE} \href{http://cdsweb.cern.ch/record/687274}{1997/002}. 917 \bibitem{bib:F rog} L. Quertenmont, V. Roberfroid, \textbf{CMS CR} \href{http://cms.cern.ch/iCMS/jsp/openfile.jsp?type=CR&year=2009&files=CR2009_028.pdf}{2009/028}, arXiv:\href{http://arxiv.org/abs/0901.2718}{0901.2718v1}[hep-ex].916 \bibitem{bib:FROG} L. Quertenmont, V. Roberfroid, \textbf{CMS CR} \href{http://cms.cern.ch/iCMS/jsp/openfile.jsp?type=CR&year=2009&files=CR2009_028.pdf}{2009/028}, arXiv:\href{http://arxiv.org/abs/0901.2718}{0901.2718v1}[hep-ex]. 918 917 \bibitem{bib:wtphotoproduction} J. de Favereau de Jeneret, S. Ovyn, \textbf{Nucl. Phys. Proc. Suppl.} \href{http://dx.doi.org/10.1016/j.nuclphysbps.2008.07.040}{179-180 (2008)} \href{http://dx.doi.org/10.1016/j.nuclphysbps.2008.07.040}{277-284}; S. Ovyn, J. de Favereau de Jeneret, \href{http://dx.doi.org/10.1393/ncb/i2008-10684-5}{Nuovo Cimento B}, arXiv:0806.4841[hep-ph]. 919 918 … … 933 932 \section{User manual} 934 933 935 The available \texttt{C++}-code is compressed in a zipped tar file which contains everything needed to run the \text sc{Delphes} package, assuming a running \textsc{root} installation. The package includes \texttt{ExRootAnalysis}~\citep{bib:ExRootAnalysis}, \textsc{Hector}~\citep{bib:Hector}, \textsc{FastJet}~\citep{bib:FastJet}, and \textsc{Frog}~\citep{bib:Frog}, as well as the conversion codes to read standard \mbox{\textsc{s}td\textsc{hep}} input files (\texttt{mcfio} and \texttt{stdhep})~\citep{bib:mcfio} and \textsc{HepMC}~\citep{bib:hepmc}.936 In order to visualise the events with the \textsc{F rog} software, a few additional external libraries may be required, as explained in \href{http://projects.hepforge.org/frog/}{http://projects.hepforge.org/frog/}.934 The available \texttt{C++}-code is compressed in a zipped tar file which contains everything needed to run the \textit{Delphes} package, assuming a running \textsc{ROOT} installation. The package includes \texttt{ExRootAnalysis}~\citep{bib:ExRootAnalysis}, \textit{Hector}~\citep{bib:hector}, FastJet~\citep{bib:FASTJET}, and \textsc{FROG}~\citep{bib:FROG}, as well as the conversion codes to read standard \mbox{StdHEP} input files (\texttt{mcfio} and \texttt{stdhep})~\citep{bib:mcfio} and HepMC~\citep{bib:hepmc}. 935 In order to visualise the events with the \textsc{FROG} software, a few additional external libraries may be required, as explained in \href{http://projects.hepforge.org/FROG/}{http://projects.hepforge.org/FROG/}. 937 936 938 937 \subsection{Getting started} 939 938 940 In order to run \text sc{Delphes} on your system, first download its sources and compile them:\\939 In order to run \textit{Delphes} on your system, first download its sources and compile them:\\ 941 940 \texttt{wget http://www.fynu.ucl.ac.be/users/s.ovyn/Delphes/files/Delphes\_V\_*.tar.gz}\\ 942 Replace the \texttt{*} symbol by the proper version number\footnote{Refer to the download page on the \text sc{Delphes} website \href{http://www.fynu.ucl.ac.be/users/s.ovyn/Delphes/download.html}{http://www.fynu.ucl.ac.be/users/s.ovyn/Delphes/download.html}. Current version of \textsc{Delphes}for this manual is V 1.8 (July 2009)}.943 944 \begin{quote} 945 \begin{verbatim} 946 me@mylaptop:~$ tar -xvf Delphes_V_*.tar.gz 941 Replace the \texttt{*} symbol by the proper version number\footnote{Refer to the download page on the \textit{Delphes} website \href{http://www.fynu.ucl.ac.be/users/s.ovyn/Delphes/download.html}{http://www.fynu.ucl.ac.be/users/s.ovyn/Delphes/download.html}. Current version of Delphes for this manual is V 1.8 (July 2009)}. 942 943 \begin{quote} 944 \begin{verbatim} 945 me@mylaptop:~$ tar -xvf Delphes_V_*.tar.gz 947 946 me@mylaptop:~$ cd Delphes_V_*.* 948 947 me@mylaptop:~$ ./genMakefile.tcl > Makefile … … 950 949 \end{verbatim} 951 950 \end{quote} 952 Due to the large number of external utilities, the number of printed lines during the compilation can be high. The user should not pay attention to possible warning messages, which are due to the external packages used by \text sc{Delphes}. When compilation is completed, the following message is printed:951 Due to the large number of external utilities, the number of printed lines during the compilation can be high. The user should not pay attention to possible warning messages, which are due to the external packages used by \textit{Delphes}. When compilation is completed, the following message is printed: 953 952 \begin{quote} 954 953 \begin{verbatim} … … 958 957 \end{quote} 959 958 960 \subsection{Running \text sc{Delphes} on your events}961 962 In this sub-appendix, we will explain how to use \text sc{Delphes} to perform a fast simulation of a general-purpose detector on your event files. The first step to use \textsc{Delphes} is to create the list of input event files (e.g.\ {\verb inputlist.list }). It is important to notice that all the files comprised in the list file should have the same of extension (\texttt{*.hep}, \texttt{*.lhe}, \texttt{*.hepmc} or \texttt{*.root}). In the simplest way to run \textsc{Delphes}, you need this input file and you need to specify the name of the output file that will contain the generator-level data (\texttt{GEN} tree), the analysis data objects after reconstruction (\texttt{Analysis} tree), and the results of the trigger emulation (\texttt{Trigger} tree).959 \subsection{Running \textit{Delphes} on your events} 960 961 In this sub-appendix, we will explain how to use \textit{Delphes} to perform a fast simulation of a general-purpose detector on your event files. The first step to use \textit{Delphes} is to create the list of input event files (e.g.\ {\verb inputlist.list }). It is important to notice that all the files comprised in the list file should have the same of extension (\texttt{*.hep}, \texttt{*.lhe}, \texttt{*.hepmc} or \texttt{*.root}). In the simplest way to run \textit{Delphes}, you need this input file and you need to specify the name of the output file that will contain the generator-level data (\texttt{GEN} tree), the analysis data objects after reconstruction (\texttt{Analysis} tree), and the results of the trigger emulation (\texttt{Trigger} tree). 963 962 964 963 \begin{quote} … … 970 969 \subsubsection{Setting up the configuration} 971 970 972 The program is driven by two datacards (default cards are {\verb data/DetectorCard.dat } and {\verb data/TriggerCard.dat }) which allow the user to choose among a large spectrum of running conditions. Please note that if the user does not provide these datacards, the running will be done using the default parameters defined in the constructor of the class \texttt{RESOLution} (see next). If you choose a different detector or running configuration, you will need to edit the datacards accordingly. Detector and trigger cards are provided in the \texttt{data/} subdirectory for the \textsc{ cms} and \textsc{atlas} experiments.971 The program is driven by two datacards (default cards are {\verb data/DetectorCard.dat } and {\verb data/TriggerCard.dat }) which allow the user to choose among a large spectrum of running conditions. Please note that if the user does not provide these datacards, the running will be done using the default parameters defined in the constructor of the class \texttt{RESOLution} (see next). If you choose a different detector or running configuration, you will need to edit the datacards accordingly. Detector and trigger cards are provided in the \texttt{data/} subdirectory for the \textsc{CMS} and \textsc{ATLAS} experiments. 973 972 974 973 \begin{enumerate} 975 974 \item{\bf The detector card } 976 It contains all pieces of information needed to run \text sc{Delphes}:975 It contains all pieces of information needed to run \textit{Delphes}: 977 976 \begin{itemize} 978 977 \item detector parameters, including calorimeter and tracking coverage and resolutions, transverse energy thresholds for object reconstruction and jet algorithm parameters. 979 \item six flags ({\verb FLAG_bfield }, {\verb FLAG_vfd }, {\verb FLAG_RP }, {\verb FLAG_trigger }, {\verb FLAG_ frog } and {\verb FLAG_lhco }), should be set in order to configure the magnetic field propagation, the very forward detectors simulation, the use of very forward taggers, the trigger selection, the preparation for \textsc{Frog} display and the creation of an output file in \texttt{*.lhco} text format (respectively).978 \item six flags ({\verb FLAG_bfield }, {\verb FLAG_vfd }, {\verb FLAG_RP }, {\verb FLAG_trigger }, {\verb FLAG_FROG } and {\verb FLAG_LHCO }), should be set in order to configure the magnetic field propagation, the very forward detectors simulation, the use of very forward taggers, the trigger selection, the preparation for \textsc{FROG} display and the creation of an output file in \texttt{*.LHCO} text format (respectively). 980 979 \end{itemize} 981 980 … … 1105 1104 FLAG_RP 1 //1 to run the very forward detectors else 0 1106 1105 FLAG_trigger 1 //1 to run the trigger selection else 0 1107 FLAG_ frog1 //1 to run the FROG event display1108 FLAG_ lhco1 //1 to run the LHCO1106 FLAG_FROG 1 //1 to run the FROG event display 1107 FLAG_LHCO 1 //1 to run the LHCO 1109 1108 1110 1109 # In case BField propagation allowed … … 1125 1124 \begin{quote} 1126 1125 \begin{verbatim} 1127 # Hectorparameters1126 #\textit{Hector} parameters 1128 1127 RP_220_s 220 // distance of the RP to the IP, in meters 1129 1128 RP_220_x 0.002 // distance of the RP to the beam, in meters … … 1132 1131 RP_beam1Card data/LHCB1IR5_v6.500.tfs // beam optics file, beam 1 1133 1132 RP_beam2Card data/LHCB2IR5_v6.500.tfs // beam optics file, beam 2 1134 RP_IP_name IP5 // tag for IP in Hector; 'IP1' for ATLAS1133 RP_IP_name IP5 // tag for IP in \textit{Hector} ; 'IP1' for ATLAS 1135 1134 RP_offsetEl_x 0.097 // horizontal separation between both beam, in meters 1136 1135 RP_offsetEl_y 0 // vertical separation between both beam, in meters … … 1143 1142 1144 1143 # In case FROG event display allowed 1145 NEvents_F rog1001144 NEvents_FROG 100 1146 1145 # Number of events to process 1147 1146 NEvents -1 // -1 means 'all' … … 1154 1153 1155 1154 In general, energies, momenta and masses are expressed in GeV, GeV$/c$, GeV$/c^2$ respectively, and magnetic fields in T. 1156 Geometrical extension are often referred in terms of pseudorapidity $\eta$, as the detectors are supposed to be symmetric in $\phi$. From version 1.8 onwards, the number of events to run is also be included in the detector card (\texttt{NEvents}). For version 1.7 and earlier, the parameters related to the calorimeter endcaps (\texttt{CEN\_max\_calo\_ec}, \texttt{ELG\_Sec}, \texttt{ELG\_Nec}, \texttt{ELG\_Cec}, \texttt{HAD\_Sec}, \texttt{HAD\_Nec} and \texttt{HAD\_Cec}) did not exist in the detector cards; in addition, some other variables had different names (\texttt{HAD\_Scen} was \texttt{HAD\_Sfcal}, \texttt{HAD\_Ncen} was \texttt{HAD\_Nfcal}, \texttt{HAD\_Ccen} was \texttt{HAD\_Cfcal}, \texttt{HAD\_Sfwd} was \texttt{HAD\_Shf}, \texttt{HAD\_Nfwd} was \texttt{HAD\_Nhf}, \texttt{HAD\_Cfwd} was \texttt{HAD\_Chf}). However, these cards are still completely compatible with new versions of \text sc{Delphes}. In such a case, the calorimeter endcaps are simply assumed to be located at the edge of the central calorimeter volumes, with the same resolution values.1155 Geometrical extension are often referred in terms of pseudorapidity $\eta$, as the detectors are supposed to be symmetric in $\phi$. From version 1.8 onwards, the number of events to run is also be included in the detector card (\texttt{NEvents}). For version 1.7 and earlier, the parameters related to the calorimeter endcaps (\texttt{CEN\_max\_calo\_ec}, \texttt{ELG\_Sec}, \texttt{ELG\_Nec}, \texttt{ELG\_Cec}, \texttt{HAD\_Sec}, \texttt{HAD\_Nec} and \texttt{HAD\_Cec}) did not exist in the detector cards; in addition, some other variables had different names (\texttt{HAD\_Scen} was \texttt{HAD\_Sfcal}, \texttt{HAD\_Ncen} was \texttt{HAD\_Nfcal}, \texttt{HAD\_Ccen} was \texttt{HAD\_Cfcal}, \texttt{HAD\_Sfwd} was \texttt{HAD\_Shf}, \texttt{HAD\_Nfwd} was \texttt{HAD\_Nhf}, \texttt{HAD\_Cfwd} was \texttt{HAD\_Chf}). However, these cards are still completely compatible with new versions of \textit{Delphes}. In such a case, the calorimeter endcaps are simply assumed to be located at the edge of the central calorimeter volumes, with the same resolution values. 1157 1156 1158 1157 \item{\bf The trigger card } 1159 1158 1160 This card contains the definitions of all trigger-bits. Cuts can be applied on the transverse momentum $p_T$ of electrons, muons, jets, $\tau$-jets, photons and the missing transverse energy. The following codes should be used so that \text sc{Delphes} can correctly translate the input list of trigger-bits into selection algorithms:1159 This card contains the definitions of all trigger-bits. Cuts can be applied on the transverse momentum $p_T$ of electrons, muons, jets, $\tau$-jets, photons and the missing transverse energy. The following codes should be used so that \textit{Delphes} can correctly translate the input list of trigger-bits into selection algorithms: 1161 1160 1162 1161 \begin{quote} … … 1177 1176 Each line in the trigger datacard is allocated to exactly one trigger-bit and starts with the name of the corresponding trigger. 1178 1177 Logical combination of several conditions is also possible. If the trigger-bit requires the presence of multiple identical objects, the order of their $p_T$ thresholds is very important: they must be defined in \textit{decreasing} order. The transverse momentum $p_T$ is expressed in \mbox{GeV/$c$}. Finally, the different requirements on the objects must be separated by a {\verb && } flag. 1179 The default trigger card can be found in the data repository of \text sc{Delphes} (\texttt{data/TriggerCard.dat}), as well as for both \textsc{cms} and \textsc{atlas} experiments at the \textsc{lhc}.1178 The default trigger card can be found in the data repository of \textit{Delphes} (\texttt{data/TriggerCard.dat}), as well as for both \textsc{CMS} and \textsc{ATLAS} experiments at the \textsc{LHC}. 1180 1179 An example of trigger table consistent with the previous rules is given here: 1181 1180 \begin{quote} … … 1191 1190 1192 1191 First, create the detector and trigger cards (\texttt{data/DetectorCard.dat} and \texttt{data/TriggerCard.dat}). \\ 1193 Then, create a text file containing the list of input files that will be used by \text sc{Delphes} (with extension \texttt{*.lhe}, \texttt{*.hepmc}, \texttt{*.root} or \texttt{*.hep}).1192 Then, create a text file containing the list of input files that will be used by \textit{Delphes} (with extension \texttt{*.lhe}, \texttt{*.hepmc}, \texttt{*.root} or \texttt{*.hep}). 1194 1193 To run the code, type the following command (in one line) 1195 1194 \begin{quote} 1196 1195 \begin{verbatim} 1197 me@mylaptop:~$ ./Delphes inputlist.list OutputRootFileName.root 1196 me@mylaptop:~$ ./Delphes inputlist.list OutputRootFileName.root 1198 1197 data/DetectorCard.dat data/TriggerCard.dat 1199 1198 \end{verbatim} … … 1213 1212 1214 1213 1215 \subsection{Getting the \text sc{Delphes} information}1216 1217 \subsubsection{Contents of the \text sc{Delphes} ROOT trees}1218 1219 The \text sc{Delphes} output file (\texttt{*.root}) is subdivided into three \textit{trees}, corresponding to generator-level data, analysis-object data and trigger output. These \textit{trees} are structures that organise the output data into \textit{branches} containing data (or \textit{leaves}) related with each others, like the kinematics properties ($E$, $p_x$, $\eta$, $\ldots$) of a given particle.1214 \subsection{Getting the \textit{Delphes} information} 1215 1216 \subsubsection{Contents of the \textit{Delphes} ROOT trees} 1217 1218 The \textit{Delphes} output file (\texttt{*.root}) is subdivided into three \textit{trees}, corresponding to generator-level data, analysis-object data and trigger output. These \textit{trees} are structures that organise the output data into \textit{branches} containing data (or \textit{leaves}) related with each others, like the kinematics properties ($E$, $p_x$, $\eta$, $\ldots$) of a given particle. 1220 1219 1221 1220 Here is the exhaustive list of \textit{branches} availables in these \textit{trees}, together with their corresponding physical objet and \texttt{ExRootAnalysis} C++ class name: 1222 1221 \begin{quote} 1223 1222 \begin{tabular}{lll} 1224 {\bf GEN \textsc{tree}} & &\\1223 \textbf{GEN \texttt{Tree}} & &\\ 1225 1224 ~~~Particle & generator particles from \textsc{hepevt} & {\verb GenParticle }\\ 1226 1225 \multicolumn{3}{l}{}\\ 1227 {\bf Trigger \textsc{tree}} & &\\1226 \textbf{Trigger \texttt{Tree}} & &\\ 1228 1227 ~~~TrigResult & Acceptance of different trigger-bits & {\verb TRootTrigger }\\ 1229 1228 \multicolumn{3}{l}{}\\ 1230 {\bf Analysis \textsc{tree}} & & \\1229 \textbf{Analysis \texttt{Tree}} & & \\ 1231 1230 ~~~Tracks & Collection of tracks & {\verb TRootTracks }\\ 1232 1231 ~~~CaloTower & Calorimetric towers & {\verb TRootCalo }\\ … … 1242 1241 \end{tabular} 1243 1242 \end{quote} 1244 The third column shows the names of the corresponding classes to be written in a \textsc{ root} tree.1243 The third column shows the names of the corresponding classes to be written in a \textsc{ROOT} tree. 1245 1244 The bin number in the unique leaf in the \texttt{trigger} tree (namely, \texttt{TrigResult.Accepted}) corresponds to the trigger number in the provided list. In addition, the result of the global trigger decision upon each event (i.e.\ the logical \texttt{OR} of all trigger conditions) is stored in the first bin (number 0) of this leaf. 1246 1245 In \texttt{Analysis} tree, all classes except \texttt{TRootTracks}, \texttt{TRootCalo}, \texttt{TRootTrigger}, \texttt{TRootETmis} and \texttt{TRootRomanPotHits} inherit from the class \texttt{TRootParticle} which includes the following data members (stored as \textit{leaves} in \textit{branches} of the \textit{trees}): … … 1329 1328 \end{quote} 1330 1329 1331 The hits in very forward detector (\textsc{ zdc, rp220, fp420}) have some common data. In particular, the \texttt{side} variable tells in which detector (left:-1 or right:+1 of the interaction point) the hit has been seen. Moreover, some generator level data is provided for information, as the correspondance with the contents of the \texttt{GEN} tree is not possible. These generator-level data correspond to the particle kinematics (energy, momentum, angle) and identification (pid).1330 The hits in very forward detector (\textsc{ZDC, RP220, FP420}) have some common data. In particular, the \texttt{side} variable tells in which detector (left:-1 or right:+1 of the interaction point) the hit has been seen. Moreover, some generator level data is provided for information, as the correspondance with the contents of the \texttt{GEN} tree is not possible. These generator-level data correspond to the particle kinematics (energy, momentum, angle) and identification (pid). 1332 1331 1333 1332 \begin{quote} … … 1369 1368 1370 1369 1371 \subsection{Running an analysis on your \text sc{Delphes} events}1372 1373 To analyse the \textsc{ root} ntuple produced by \textsc{Delphes}, the simplest way is to use the {\verb Analysis_Ex.cpp } code which is coming in the {\verb Examples } repository of \textsc{Delphes}. Note that all of this is optional and done to facilitate the analyses, as the output from \textsc{Delphes} is viewable with the standard \textsc{root} \texttt{TBrowser} and can be analysed using the \texttt{MakeClass} facility.1374 As an example, here is a simple overview of a \texttt{myoutput.root} file created by \text sc{Delphes}:1370 \subsection{Running an analysis on your \textit{Delphes} events} 1371 1372 To analyse the \textsc{ROOT} ntuple produced by \textit{Delphes}, the simplest way is to use the {\verb Analysis_Ex.cpp } code which is coming in the {\verb Examples } repository of \textit{Delphes}. Note that all of this is optional and done to facilitate the analyses, as the output from \textit{Delphes} is viewable with the standard \textsc{ROOT} \texttt{TBrowser} and can be analysed using the \texttt{MakeClass} facility. 1373 As an example, here is a simple overview of a \texttt{myoutput.root} file created by \textit{Delphes}: 1375 1374 \begin{quote} 1376 1375 \begin{verbatim} … … 1440 1439 For more information, refer to ROOT documentation. Moreover, an example of code (based on the output of \texttt{MakeClass}) is provided in the \texttt{Examples/} directory. 1441 1440 1442 To run the \texttt{Examples/Analysis\_Ex.cpp} code, the two following arguments are required: a text file containing the input \text sc{Delphes} \textsc{root} files to run, and the name of the output \textsc{root} file.1441 To run the \texttt{Examples/Analysis\_Ex.cpp} code, the two following arguments are required: a text file containing the input \textit{Delphes} \texttt{root} files to run, and the name of the output \texttt{root} file. 1443 1442 \begin{quote} 1444 1443 \begin{verbatim} … … 1449 1448 1450 1449 \subsubsection{Adding the trigger information} 1451 The \texttt{Examples/Trigger\_Only.cpp} code permits to run the trigger selection separately from the general detector simulation on output \text sc{Delphes} root files. A \textsc{Delphes} root file is mandatory as an input argument for the \texttt{Trigger\_Only} routine. The new \textit{tree} containing the trigger result data will be appended to this file.1450 The \texttt{Examples/Trigger\_Only.cpp} code permits to run the trigger selection separately from the general detector simulation on output \textit{Delphes} root files. A \textit{Delphes} \texttt{root} file is mandatory as an input argument for the \texttt{Trigger\_Only} routine. The new \textit{tree} containing the trigger result data will be appended to this file. 1452 1451 The trigger datacard is also necessary. To run the code: 1453 1452 \begin{quote} … … 1460 1459 1461 1460 \begin{itemize} 1462 \item If the { \verb FLAG_ frog } was switched on in the smearing card, two files have been created during the running of \textsc{Delphes}: {\verb DelphesToFrog.vis } and {\verb DelphesToFrog.geom }. They contain all the needed pieces of information to run \textsc{frog}.1463 \item To display the events and the geometry, you first need to compile \textsc{F rog}. Go to the {\verb Utilities/FROG } and type {\verb make }. This compilation is done once for all, with this geometry (i.e.\ as long as the \texttt{*vis} and \texttt{*geom} files do not change).1461 \item If the { \verb FLAG_FROG } was switched on in the smearing card, two files have been created during the running of \textit{Delphes}: \texttt{DelphesToFROG.vis} and \texttt{DelphesToFROG.geom }. They contain all the needed pieces of information to run \textsc{FROG}. 1462 \item To display the events and the geometry, you first need to compile \textsc{FROG}. Go to the {\verb Utilities/FROG } and type {\verb make }. This compilation is done once for all, with this geometry (i.e.\ as long as the \texttt{*vis} and \texttt{*geom} files do not change). 1464 1463 \item Go back into the main directory and type 1465 1464 \begin{quote} 1466 \texttt{me@mylaptop:~\$ ./Utilities/FROG/ frog}1465 \texttt{me@mylaptop:~\$ ./Utilities/FROG/FROG} 1467 1466 \end{quote} 1468 1467 \end{itemize} 1469 1468 1470 1469 \subsection{LHCO file format} 1471 The \texttt{* lhco} file format is a text-\textsc{ascii} data format briefly discussed here. An exhaustive description is provided on \href{http://v1.jthaler.net/olympicswiki}{http://v1.jthaler.net/olympicswiki}. This section is based on this webpage.1472 Only final high-level objects are available in the \texttt{ lhco} format, and their properties are arranged in columns. Each row corresponds to an object in the event and all events are written after each other. Comment-lines starts with a hash \texttt{\#} symbol.1470 The \texttt{*LHCO} file format is a text-\textsc{ASCII} data format briefly discussed here. An exhaustive description is provided on \href{http://v1.jthaler.net/olympicswiki}{http://v1.jthaler.net/olympicswiki}. This section is based on this webpage. 1471 Only final high-level objects are available in the \texttt{LHCO} format, and their properties are arranged in columns. Each row corresponds to an object in the event and all events are written after each other. Comment-lines starts with a hash \texttt{\#} symbol. 1473 1472 1474 1473 \begin{verbatim} … … 1484 1483 \end{verbatim} 1485 1484 Each row in an event starts with a unique number (i.e.\ in first column). 1486 Row \texttt{0} contains the event number (here: \texttt{57}) and some trigger information (here: \texttt{0}. This very particular trigger encoding is not implemented in \text sc{Delphes}.).1485 Row \texttt{0} contains the event number (here: \texttt{57}) and some trigger information (here: \texttt{0}. This very particular trigger encoding is not implemented in \textit{Delphes}.). 1487 1486 Subsequent rows list the reconstructed high-level objects. 1488 1487 Each row is organised in columns, which details the object kinematics as well as more specific information, such as isolation criteria or $b$-tagging. … … 1528 1527 1529 1528 \paragraph{Warning} 1530 Inherently to the data format itself, the \texttt{* lhco} output contains only a fraction of the available data. Moreover, dealing with text file may have various drawbacks, such as the output file size and the time needed for its creation. Whenever possible, working on the \texttt{*root} output file should be preferred.1529 Inherently to the data format itself, the \texttt{*LHCO} output contains only a fraction of the available data. Moreover, dealing with text file may have various drawbacks, such as the output file size and the time needed for its creation. Whenever possible, working on the \texttt{*root} output file should be preferred. 1531 1530 1532 1531 \end{document}
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