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Changeset 117 in svn for trunk/paper/notes.tex


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Timestamp:
Jan 1, 2009, 7:19:08 PM (16 years ago)
Author:
Xavier Rouby
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update

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  • trunk/paper/notes.tex

    r116 r117  
    22%\usepackage[english]{babel}
    33\usepackage[ansinew]{inputenc}
     4\usepackage{abstract}
    45
    56\usepackage{amsmath}
     
    9495%The simulation package proceeds in two stages. The first part is executed on the generated events. ``Particle-level" informations are read from input files and stored in a {\it \textsc{gen}} \textsc{root} tree.
    9596
    96 Three formats of input files can currently be used as input in \textsc{Delphes}\footnote{The corresponding code can be found in the \texttt{HEPEVTConverter}, \texttt{LHEFConverter } and \texttt{STDHEPConverter} classes.}. In order to process events from many different generators, the standard Monte Carlo event structure \mbox{\textsc{s}td\textsc{hep}} can be used as an input. Besides, \textsc{Delphes} can also provide detector response for events read in ``Les Houches Event Format'' (\textsc{lhef}) and \textsc{root} files obtained using the \textbf{h2root} utility from the \textsc{root} framework~\cite{bib:root}.
     97Three formats of input files can currently be used as input in \textsc{Delphes}\footnote{\texttt{[code] }See the \texttt{HEPEVTConverter}, \texttt{LHEFConverter} and \texttt{STDHEPConverter} classes.}. In order to process events from many different generators, the standard Monte Carlo event structure \mbox{\textsc{s}td\textsc{hep}} can be used as an input. Besides, \textsc{Delphes} can also provide detector response for events read in ``Les Houches Event Format'' (\textsc{lhef}) and \textsc{root} files obtained using the \textbf{h2root} utility from the \textsc{root} framework~\cite{bib:root}.
    9798%Afterwards, \textsc{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.
    9899
     
    131132
    132133
    133 The overall layout of the general purpose detector simulated by \textsc{Delphes} is shown in figure \ref{fig:GenDet}. A central tracking system is surrounded by an electromagnetic and a hadron calorimeters (\textsc{ecal} and \textsc{hcal}, resp.). A forward calorimeter ensures a larger geometric coverage for the measurement of the missing transverse energy. The fast simulation of the detector response takes into account geometrical acceptance of sub-detectors and their finite resolution, as defined in the smearing data card\footnote{See the \texttt{RESOLution} class.}.
    134 If no such file is provided, predifined values are used. The coverage of the various subsystems used in the default configuration are summarized in table \ref{tab:defEta}.
     134The overall layout of the general purpose detector simulated by \textsc{Delphes} is shown in figure \ref{fig:GenDet}.
     135A central tracking system (\textsc{tracker}) is surrounded by an electromagnetic and a hadron calorimeters (\textsc{ecal} and \textsc{hcal}, resp.). 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
     136The fast simulation of the detector response takes into account geometrical acceptance of sub-detectors and their finite resolution, as defined in the smearing data card\footnote{\texttt{[code] }See the \texttt{RESOLution} class.}.
     137If no such file is provided, predifined values are used. The coverage of the various subsystems used in the default configuration are summarised in table \ref{tab:defEta}.
    135138
    136139\textcolor{red}{No smearing is applied on particle direction. (???)}\\
     
    138141\begin{table}[!h]
    139142\begin{center}
    140 \caption{Default extension in pseudorapidity $\eta$ of the different subdetectors.}
     143\caption{Default extension in pseudorapidity $\eta$ of the different subdetectors.
     144The corresponding parameter name, in the smearing card, is given. \vspace{0.5cm}}
    141145\begin{tabular}[!h]{lll}
    142146\hline
    143 Tracking    & {\verb CEN_max_tracker } & $0.0 \leq |\eta| \leq 2.5$\\
    144 Calorimeters & {\verb CEN_max_calo_cen } & $0.0 \leq |\eta| \leq 3.0$\\
    145             & {\verb CEN_max_calo_fwd } & $3.0 \leq |\eta| \leq5.0$\\
    146 Muon        & {\verb CEN_max_mu } & $0.0 \leq |\eta| \leq 2.4$\\\hline
     147\textsc{tracker} & {\verb CEN_max_tracker } & $0.0 \leq |\eta| \leq 2.5$\\
     148\textsc{ecal}, \textsc{hcal} & {\verb CEN_max_calo_cen } & $0.0 \leq |\eta| \leq 3.0$\\
     149\textsc{fcal} & {\verb CEN_max_calo_fwd } & $3.0 \leq |\eta| \leq5.0$\\
     150\textsc{muon} & {\verb CEN_max_mu } & $0.0 \leq |\eta| \leq 2.4$\\\hline
    147151\end{tabular}
    148152\label{tab:defEta}
     
    150154\end{table}
    151155
    152 \subsection{Simulation of calorimeters response}
    153 
    154 The energy of all particle considered as stable in the generator particle list are smeared according to a resolution depending which sub-calorimeter is assumed to be used for the energy measurement. For particles with a short lifetime such as the $K_s$, the fraction of electromagnetic or hadronic energy is determined according to its decay products. The response of the each sub-calorimeter is parametrized as a function of the energy
     156\subsection{Simulation of calorimeters}
     157
     158The 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.
     159The response of each sub-calorimeter is parametrised as a function of the energy:
    155160\begin{equation}
    156161\frac{\sigma}{E} = \frac{S}{\sqrt{E}} \oplus \frac{N}{E} \oplus C,
     162\label{eq:caloresolution}
    157163\end{equation}
    158 where $S$ is the stochastic term, $N$ the noise and $C$ the constant term.\\
    159 
    160 
    161 The 4-momentum $p^\mu$ are smeared with a parametrisation directly derived from the detector techinal designs\footnote{The response of the detector is applied to the electromagnetic and the hadronic particles through the \texttt{SmearElectron} and \texttt{SmearHadron} functions.}.
    162 In the default parametrisation, the calorimeter is assumed to cover the pseudorapidity range $|\eta|<3$ and consists in an electromagnetic and an hadronic part. Coverage between pseudorapidities of $3.0$ and $5.0$ is provided by a forward calorimeter. The response of this calorimeter can be different for electrons and hadrons. The default values of the stochastic, noisy and constant terms are given in table \ref{tab:defResol}.\\
     164where $S$, $N$ and $C$ are the \textit{stochastic}, \textit{noise} and \textit{constant} terms, respectively.\\
     165
     166
     167The particle 4-momentum $p^\mu$ are smeared with a parametrisation directly derived from the detector techinal 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.}.
     168In the default parametrisation, the calorimeter is assumed to cover the pseudorapidity range $|\eta|<3$ and consists in an electromagnetic and an hadronic part. 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.
     169Muons and neutrinos are assumed no to interact with the calorimeters\footnote{In the current \textsc{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 subsequently be handled with care.}.
     170The default values of the stochastic, noisy and constant terms are given in Table~\ref{tab:defResol}.\\
    163171
    164172\begin{table}[!h]
    165173\begin{center}
    166 \caption{Default values for the resolution of the central and forward calorimeter. The corresponding parameter name, in the smearing card, is given.}
     174\caption{Default values for the resolution of the central and forward calorimeters. Resolution is parametrised by the \textit{stochastic} ($S$), \textit{noise} ($N$) and \textit{constant} ($C$) terms (Eq.~\ref{eq:caloresolution}).
     175The corresponding parameter name, in the smearing card, is given. \vspace{0.5cm}}
    167176\begin{tabular}[!h]{lclc}
    168177\hline
    169178\multicolumn{2}{c}{Resolution Term}   & Card flag & Value\\\hline
    170  \multicolumn{4}{l}{Central \textsc{ecal}} \\
     179 \multicolumn{4}{l}{\textsc{ecal}} \\
    171180        & $S$ & {\verb ELG_Scen }  & $0.05$ \\
    172181        & $N$ & {\verb ELG_Ncen }  & $0.25$ \\
    173182        & $C$ & {\verb ELG_Ccen }  & $0.0055$ \\
    174  \multicolumn{4}{l}{Forward \textsc{ecal}} \\
     183 \multicolumn{4}{l}{\textsc{fcal}, electromagnetic part} \\
    175184        & $S$ & {\verb ELG_Sfwd }  & $2.084$ \\
    176         & $N$ & {\verb ELG_Nfwd }  & $0.0$ \\
     185        & $N$ & {\verb ELG_Nfwd }  & $0$ \\
    177186        & $C$ & {\verb ELG_Cfwd }  & $0.107$ \\
    178  \multicolumn{4}{l}{Central \textsc{hcal}} \\
     187 \multicolumn{4}{l}{\textsc{hcal}} \\
    179188        & $S$ & {\verb HAD_Shcal } & $1.5$ \\
    180         & $N$ & {\verb HAD_Nhcal } & $0.$\\
     189        & $N$ & {\verb HAD_Nhcal } & $0$\\
    181190        & $C$ & {\verb HAD_Chcal } & $0.05$\\
    182  \multicolumn{4}{l}{Forward \textsc{hcal}} \\
     191 \multicolumn{4}{l}{\textsc{fcal}, hadronic part} \\
    183192        & $S$ & {\verb HAD_Shf }   & $2.7$\\
    184193        & $N$ & {\verb HAD_Nhf }   & $0$. \\
     
    190199\end{table}
    191200
    192 The energy of electron and photon particles 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 the forward calorimeter. Some long-living particles, such as the $K_s$, possessing lifetime $c\tau$ smaller than 10~mma are considering as stable particles although they decay in the calorimeters. The energy smearing of such particles is performed using the expected fraction of the energy, determined according to their decay products, that whould be deposited into the \textsc{ecal} ($E_{ecal}$) and into the \textsc{hcal} ($E_{hcal}$). Defining $F$ as the fraction of the energy leading to a \textsc{hcal} deposit, the two energy values are given by
     201The 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}.
     202Some long-living particles, such as the $K^0_s$, possessing 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
    193203\begin{equation}
    194 E_{hcal} = E \times F ~\mathrm{and}~ E_{ecal} = E \times (1-F),
     204\left\{
     205\begin{array}{l}
     206E_{\textsc{hcal}} = E \times F \\
     207E_{\textsc{ecal}} = E \times (1-F) \\
     208\end{array}
     209\right.
    195210\end{equation}
    196 where $0 \leq F \leq 1$. The electromagnetic part is handled as the electrons, while the resolution terms used for the hadronic part are {\verb HAD_Shcal }, {\verb HAD_Nhcal } and {\verb HAD_Chcal }. The resulting final energy given after the application of the smearing is then $E = E_{hcal} + E_{ecal}$.\\
     211where $0 \leq F \leq 1$. The electromagnetic part is handled as the electrons. The resulting final energy given after the application of the smearing is then $E = E_{\textsc{hcal}} + E_{\textsc{ecal}}$. For $K_S^0$ and $\Lambda$ hadrons, the energy fraction is $F$ is assumed to be worth $0.7$.\\
    197212
    198213\subsection{Calorimetric towers}
    199214
    200 All undecayed particles, except muons and neutrinos are producing a calorimetric tower.
     215The smallest unit for geometrical sampling of the calorimeters is a \textit{tower}.
     216All undecayed particles, except muons and neutrinos produce a calorimetric tower, either in \textsc{ecal}, in \textsc{hcal} or \textsc{fcal}.
    201217A calorimetric tower are just the smallest unit in $\eta \times \phi$ for the segmentation of the energy measurement. As the detector is assumed to be symmetric in $\phi$ and with respect to the $(x,y)$ plane, the smearing 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.
    202218The calorimeters are then segmented into towers, that directly enter in the calculation of the missing transverse energy.
    203 No longitudinal segmentation is available in the simulated calorimeters.
     219No longitudinal segmentation is available in the simulated calorimeters. No sharing between towers is implemented when particles enter a tower very close to its geometrical edge.
    204220
    205221
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