| 1 | |
| 2 | |
| 3 | == LHC Phenomenology with MadGraph == |
| 4 | ==== Universita' di Milano, May 25-26, 2010 ==== |
| 5 | |
| 6 | === Authors === |
| 7 | |
| 8 | * Fabio Maltoni (lecturer) |
| 9 | === Lectures === |
| 10 | |
| 11 | An abstract and plan is available [attachment:program-milan-mg.pdf here]. |
| 12 | |
| 13 | Find the pdf of the 3 x 1h+1h hours lecture: |
| 14 | |
| 15 | * [attachment:lecture1v1.pdf Lecture 1] : The big picture and matrix element generators. |
| 16 | * [attachment:lecture2v1.pdf Lecture 2] : Cross sections and parton level event generation. |
| 17 | * [attachment:lecture3v1.pdf Lecture 3] : Simulation of a complex final state. |
| 18 | === References === |
| 19 | |
| 20 | * [http://www.hep.phy.cam.ac.uk/theory/webber/QCDbook.html QCD and Collider Physics] by Keith Ellis, James Stirling, Bryan Webber (Cambridge Monographs, 1996). |
| 21 | * [:FurtherReading:Perspectives on LHC physics, Ed. by G. Kane and A. Pierce]. |
| 22 | === MadGraph Exercises === |
| 23 | |
| 24 | Here we present simple exercises to familiarize with MadGraph software and also for more interesting applications to LHC phenomenology. |
| 25 | |
| 26 | A summary of the pheno exercises can be found [attachment:Exercises.pdf here]. |
| 27 | ==== ---+++ Lecture 1: Familiarize with Software.MadGraph ==== |
| 28 | |
| 29 | * Logon to the Software.MadGraph web site and register: http://madgraph.hep.uiuc.edu. |
| 30 | * Register with a valid e-mail address |
| 31 | * Feynman diagrams. Generate a few processes (with different QED + QCD couplings) trying to guess which diagrams appear: |
| 32 | * uu~>tt~ |
| 33 | * gg>tt~ |
| 34 | * gg>tt~h |
| 35 | * uu~>tt~bb~ |
| 36 | * Subprocess identification. List all subprocesses contributing to: |
| 37 | * pp>h>tt~bb~ |
| 38 | * pp>tt~bb~ |
| 39 | * pp>tt~jj |
| 40 | * Look at the new physics models and check the particle and interactions content. |
| 41 | * Advanced: Download the MG/ME package and play with the standalone version. |
| 42 | * [:SimpleKinematics:Kinematics at the LHC]: refresh the kinematics of an hadron collider. |
| 43 | ==== Lecture 2: Calculate cross sections and generate events ==== |
| 44 | |
| 45 | Generate events for a few selected processes and look at the plots: |
| 46 | |
| 47 | * ttbar production with decays: pp>tt~>bb~mu+e-ve~vm |
| 48 | * VV production: pp>VV> leptons, with V=Z,W. |
| 49 | * Single top + Higgs: pp>tHj (QCD=0, QED=3, j=gudsc,p=gudscb). Show that there is a large negative interference between the diagrams. |
| 50 | * gg>H>WW |
| 51 | * Weak boson fusion |
| 52 | |
| 53 | Some phenomenological applications (at the parton level): |
| 54 | |
| 55 | * [:2Jets:Jets] : Di-jet kinematics and rates in pp collisions. |
| 56 | * [:3Jets:3 Jets] : Energy distributions in 3-jet events. |
| 57 | * [http://cp3wks05.fynu.ucl.ac.be/twiki/bin/view/Physics/WAsymm Drell-Yan] : Study the rapidity asymmetry at the Tevatron. |
| 58 | * [:tt:top production] : %$t \bar t$% production, Tevatron vs LHC. |
| 59 | * [:tprime:t' production] : %$t'$% production at the LHC. |
| 60 | ==== Lecture 3: The full simulation chain and advanced features ==== |
| 61 | |
| 62 | Try out the Analysis Tools: |
| 63 | * a Fortran-based package: Software.MadAnalysis ([http://madgraph.phys.ucl.ac.be/cgi-bin/NewProcess/download.cgi Download it here]) |
| 64 | * a Mathematica-based package: [http://www.jthaler.net/olympics/software.html Chameleon]. |
| 65 | |
| 66 | Study what is known of a SM Higgs at the LHC: |
| 67 | * Find the best prediction for Higgs production at the LHC [http://maltoni.web.cern.ch/maltoni/TeV4LHC/index.html here]. |
| 68 | * Find the Higgs branching ratios [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/CernSummerSchool08/h-br.pdf here]. |
| 69 | |
| 70 | Choose a channel and investigate signal and background: |
| 71 | 1. The 4 lepton final state: %$pp \to H\to Z Z \to e^+e^- \mu^+ \mu^-$% |
| 72 | * Signal |
| 73 | * Events: [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/h4l-signal.lhe.gz Parton Level] [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/h4l-signal.lhco.gz Detector Level] |
| 74 | * Plots: [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/h4l-signal-lhe.pdf Parton Level] [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/h4l-signal-lhco.pdf Detector Level] |
| 75 | * Background |
| 76 | * Events: [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/h4l.lhe.gz Parton Level] [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/h4l.lhco.gz Detector Level] |
| 77 | * Plots: [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/h4l-lhe.pdf Parton Level] [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/h4l-lhco.pdf Detector Level] |
| 78 | 1. The 2 lepton + missing Et final state: %$pp \to H\to W^+ W^- \to e^- \bar \nu_e \mu^+ \nu_\mu $ |
| 79 | * Signal |
| 80 | * Events: [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/hww-signal.lhe.gz Parton Level] [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/hww-signal.lhco.gz Detector Level] |
| 81 | * Plots: [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/hww-signal-lhe.pdf Parton Level] [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/hww-signal-lhco.pdf Detector Level] |
| 82 | * Background |
| 83 | * Events: [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/hww-background.lhe.gz Parton Level] [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/hww-background.lhco.gz Detector Level] |
| 84 | * Plots: [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/hww-background-lhe.pdf Parton Level] [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/hww-background-lhco.pdf Detector Level] |
| 85 | 1. Top associated production %$pp \to t\bar tH$% with %$H \to b \bar b$% |
| 86 | * Signal + Background samples: |
| 87 | * Events: [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/ttbb.lhe.gz Parton Level] [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/ttbb.lhco.gz Detector Level] |
| 88 | * Plots: [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/ttbb-lhe.pdf Parton Level] [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/DiscoverTheHiggs/ttbb-lhco.pdf Detector Level] |
| 89 | |
| 90 | === MadGraph BlackBox Challenge === |
| 91 | |
| 92 | Three "black boxes" are given, in the form of event files in the LHC Olympics format and a series of selected plots: |
| 93 | |
| 94 | * Box A : [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/Milano2010/A.lhco.gz Events] Plots: [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/Milano2010/A-lhe.pdf Parton level] [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/Milano2010/A.pdf Detector level] |
| 95 | * Box B : [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/Milano2010/B.lhco.gz Events] Plots: [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/Milano2010/B-lhe.pdf Parton level] [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/Milano2010/B.pdf Detector level] |
| 96 | * Box C : [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/Milano2010/C.lhco.gz Events] Plots: [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/Milano20102/C-lhe.pdf Parton level] [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/Milano2010/C.pdf Detector level] |
| 97 | |
| 98 | Black boxes contain only signal events. The students are asked to pair up the boxes above with the following models and also answer to the questions: |
| 99 | |
| 100 | * Model 1 : Extra Z (zp) : What its mass? Does it have Standard Model couplings to fermions? |
| 101 | * Model 2 : Heavy Scalar (h): What its mass? Is it a SM Higgs? |
| 102 | * Model 3 : Extra W (wp+ or wp-) : What its mass? Does it have Standard Model couplings to fermions? |
| 103 | |
| 104 | Useful extra information: |
| 105 | * In the plots %$H_T=\sum ||p_T^{vis}|| + E_T^{miss}$%. |
| 106 | * A SM-like Z' would decay (more or less democratically) into: jet jet (uu~,cc~,dd~,ss~,bb~), t tbar (tt~), lept+lept- (e+e-,mu+mu-,ta+ta-), neutrino anti-neutrino (ve ve~,vm vm~,vt vt~). It could also have couplings to SM W and Z, and in that case would decay in to ZZ and W+W-. |
| 107 | * An Higgs couple to particles with a strength which is proportional to the particle masses. A SM-like heavy H would decay in to t tbar (tt~), W+W-, ZZ. |
| 108 | * A SM-like W'+ would decay into: jet jet (ud~,cs~), t b (tb~), lept neutrino (e+ ve , mu+ vm, ta+ vt). It could also have couplings to SM W and Z, and in that case would decay in to ZW. |
| 109 | |
| 110 | === Monte Carlo's === |
| 111 | |
| 112 | For those interested in getting deeper into Monte Carlo techniques, here are some more exercises: |
| 113 | |
| 114 | * Write the simplest integration function based on the definition of average and error |
| 115 | * Importance sampling via an analytic transformation |
| 116 | * Von Neumann's rejection method : plain and improved |
| 117 | * Phase space for 1 -> n particles |
| 118 | * Vegas |
| 119 | * Top decay : comparison among the various methods |
| 120 | * qq -> tt production |
| 121 | |
| 122 | All exercises are presented and solved this Mathematica Notebook: [attachment:mc101.nb mc101.nb]. Reference: [http://www.slac.stanford.edu/spires/find/hep/www?eprint=hep-ph/0006269 Introduction to MC methods], by [http://wwwthep.physik.uni-mainz.de/~stefanw/ Stefan Weinzierl] |
| 123 | === Animations === |
| 124 | * [http://madgraph.hep.uiuc.edu/Event/ Interactive Flash version] Note you may want to zoom in! |
| 125 | * [http://madgraph.hep.uiuc.edu/Event/fast_collisionx6.avi Fast movie (.avi) of collision] |
| 126 | * [http://madgraph.hep.uiuc.edu/Event/collision.mov Guided movie (.mov) of collision] |
| 127 | * [http://www.youtube.com/watch?v=j50ZssEojtM LHC_Rap] |
| 128 | |
| 129 | -- Main.FabioMaltoni - 2010-05-23 |
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