Changes between Initial Version and Version 1 of Cargese2010


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  • Cargese2010

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     3== LHC Phenomenology with MadGraph ==
     4==== Cargese, July 20-31, 2010 ====
     5
     6=== Authors ===
     7
     8   * Tim Stelzer (lecturer)
     9=== Lectures ===
     10
     11Find the pdf of the 3 x 1.5 hours lecture:(available after lectures)
     12
     13   * Lecture 1: The big picture and matrix element generators.
     14   * Lecture 2: Cross sections and parton level event generation.
     15   * Lecture 3 : Simulation of a complex final state.
     16=== References ===
     17
     18   * [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).
     19   * [:FurtherReading:Perspectives on LHC physics, Ed. by G. Kane and A. Pierce].
     20=== MadGraph Exercises ===
     21
     22Here we present simple exercises to familiarize with MadGraph software and also for more interesting applications to LHC phenomenology.
     23
     24A summary of the pheno exercises can be found [attachment:Exercises.pdf here].
     25==== ---+++ Lecture 1: Familiarize with Software.MadGraph ====
     26
     27   * Logon to the Software.MadGraph web site and register: http://madgraph.hep.uiuc.edu.
     28   * Register with a valid e-mail address
     29   * Feynman diagrams. Generate a few processes (with different QED + QCD couplings) trying to guess which diagrams appear:
     30      * uu~>tt~
     31      * gg>tt~
     32      * gg>tt~h
     33      * uu~>tt~bb~
     34   * Subprocess identification. List all subprocesses contributing to:
     35      * pp>h>tt~bb~
     36      * pp>tt~bb~
     37      * pp>tt~jj
     38   * Look at the new physics models and check the particle and interactions content.
     39   * Advanced: Download the MG/ME package and play with the standalone version.
     40   * [:SimpleKinematics:Kinematics at the LHC]: refresh the kinematics of an hadron collider.
     41==== Lecture 2: Calculate cross sections and generate events ====
     42
     43Generate events for a few selected processes and look at the plots:
     44
     45   * ttbar production with decays: pp>tt~>bb~mu+e-ve~vm
     46   * VV production: pp>VV> leptons, with V=Z,W.
     47   * Single top + Higgs: pp>tHj (QCD=0, QED=3, j=gudsc,p=gudscb). Show that there is a large negative interference between the diagrams.
     48   * gg>H>WW
     49   * Weak boson fusion
     50
     51Some phenomenological applications (at the parton level):
     52
     53   * [:2Jets:Jets] : Di-jet kinematics and rates in pp collisions.
     54   * [:3Jets:3 Jets] : Energy distributions in 3-jet events.
     55   * [http://cp3wks05.fynu.ucl.ac.be/twiki/bin/view/Physics/WAsymm Drell-Yan] : Study the rapidity asymmetry at the Tevatron.
     56   * [:tt:top production] : %$t \bar t$% production, Tevatron vs LHC.
     57   * [:tprime:t' production] : %$t'$% production at the LHC.
     58==== Lecture 3: The full simulation chain and advanced features ====
     59
     60Try out the Analysis Tools:
     61   * a Fortran-based package: Software.MadAnalysis ([http://madgraph.phys.ucl.ac.be/cgi-bin/NewProcess/download.cgi Download it here])
     62   * a Mathematica-based package: [http://www.jthaler.net/olympics/software.html Chameleon].
     63
     64Study what is known of a SM Higgs at the LHC:
     65   * Find the best prediction for Higgs production at the LHC [http://maltoni.web.cern.ch/maltoni/TeV4LHC/index.html here].
     66   * Find the Higgs branching ratios [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/CernSummerSchool08/h-br.pdf here].
     67
     68Choose a channel and investigate signal and background:
     69   1. The 2 lepton + missing Et final state: %$pp \to H\to W^+ W^- \to e^- \bar \nu_e \mu^+ \nu_\mu $
     70      * Signal
     71         * 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]
     72         * 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]
     73      * Background
     74         * 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]
     75         * 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]
     76   1. Top associated production %$pp \to t\bar tH$% with %$H \to b \bar b$%
     77      * Signal + Background samples:
     78         * 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]
     79         * 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]
     80
     81=== MadGraph BlackBox Challenge ===
     82
     83Three "black boxes" are given, in the form of event files in the LHC Olympics format and a series of selected plots:
     84
     85   * 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]
     86   * 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]
     87   * 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/Milano2010/C-lhe.pdf Parton level] [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/Milano2010/C.pdf Detector level]
     88
     89Black 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:
     90
     91   * Model 1 : Extra Z (zp) : What its mass? Does it have Standard Model couplings to fermions?
     92   * Model 2 : Heavy Scalar (h): What its mass? Is it a SM Higgs?
     93   * Model 3 : Extra W (wp+ or wp-) : What its mass? Does it have Standard Model couplings to fermions?
     94
     95Useful extra information:
     96   * In the plots %$H_T=\sum ||p_T^{vis}|| + E_T^{miss}$%.
     97   * 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-.
     98   * 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.
     99   * 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.
     100
     101=== Monte Carlo's ===
     102
     103For those interested in getting deeper into Monte Carlo techniques, here are some more exercises:
     104
     105   * Write the simplest integration function based on the definition of average and error
     106   * Importance sampling via an analytic transformation
     107   * Von Neumann's rejection method : plain and improved
     108   * Phase space for 1 -> n particles
     109   * Vegas
     110   * Top decay : comparison among the various methods
     111   * qq -> tt production
     112
     113All 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]
     114=== Animations ===
     115   * [http://madgraph.hep.uiuc.edu/Event/ Interactive Flash version] Note you may want to zoom in!
     116   * [http://madgraph.hep.uiuc.edu/Event/fast_collisionx6.avi Fast movie (.avi) of collision]
     117   * [http://madgraph.hep.uiuc.edu/Event/collision.mov Guided movie (.mov) of collision]
     118   * [http://www.thedailyshow.com/watch/thu-april-30-2009/large-hadron-collider John Ellis on Daily Show]
     119
     120-- Main.TimStelzer - 2010-07-19