== LHC Phenomenology with MadGraph ==
==== Cargese, July 20-31, 2010 ====

=== Authors ===

   * Tim Stelzer (lecturer)
=== Lectures ===

Find the pdf of the 3 x 1.5 hours lecture:(available after lectures)

   * Lecture 1: The big picture and matrix element generators.
   * Lecture 2: Cross sections and parton level event generation.
   * Lecture 3 : Simulation of a complex final state.
=== References ===

   * [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).
   * [:FurtherReading:Perspectives on LHC physics, Ed. by G. Kane and A. Pierce].
=== MadGraph Exercises ===

Here we present simple exercises to familiarize with MadGraph software and also for more interesting applications to LHC phenomenology.

A summary of the pheno exercises can be found [attachment:Exercises.pdf here].
==== ---+++ Lecture 1: Familiarize with Software.MadGraph ====

   * Logon to the Software.MadGraph web site and register: http://madgraph.hep.uiuc.edu.
   * Register with a valid e-mail address
   * Feynman diagrams. Generate a few processes (with different QED + QCD couplings) trying to guess which diagrams appear: 
      * uu~>tt~
      * gg>tt~
      * gg>tt~h
      * uu~>tt~bb~
   * Subprocess identification. List all subprocesses contributing to: 
      * pp>h>tt~bb~
      * pp>tt~bb~
      * pp>tt~jj
   * Look at the new physics models and check the particle and interactions content.
   * Advanced: Download the MG/ME package and play with the standalone version.
   * [:SimpleKinematics:Kinematics at the LHC]: refresh the kinematics of an hadron collider.
==== Lecture 2: Calculate cross sections and generate events ====

Generate events for a few selected processes and look at the plots:

   * ttbar production with decays: pp>tt~>bb~mu+e-ve~vm
   * VV production: pp>VV> leptons, with V=Z,W.
   * Single top + Higgs: pp>tHj (QCD=0, QED=3, j=gudsc,p=gudscb). Show that there is a large negative interference between the diagrams.
   * gg>H>WW
   * Weak boson fusion

Some phenomenological applications (at the parton level):

   * [:2Jets:Jets] : Di-jet kinematics and rates in pp collisions.
   * [:3Jets:3 Jets] : Energy distributions in 3-jet events.
   * [http://cp3wks05.fynu.ucl.ac.be/twiki/bin/view/Physics/WAsymm Drell-Yan] : Study the rapidity asymmetry at the Tevatron.
   * [:tt:top production] : %$t \bar t$% production, Tevatron vs LHC.
   * [:tprime:t' production] : %$t'$% production at the LHC.
==== Lecture 3: The full simulation chain and advanced features ====

Try out the Analysis Tools:
   * a Fortran-based package: Software.MadAnalysis ([http://madgraph.phys.ucl.ac.be/cgi-bin/NewProcess/download.cgi Download it here])
   * a Mathematica-based package: [http://www.jthaler.net/olympics/software.html Chameleon].

Study what is known of a SM Higgs at the LHC:
   * Find the best prediction for Higgs production at the LHC [http://maltoni.web.cern.ch/maltoni/TeV4LHC/index.html here].
   * Find the Higgs branching ratios [http://cp3wks05.fynu.ucl.ac.be/twiki/pub/Physics/CernSummerSchool08/h-br.pdf here].

Choose a channel and investigate signal and background:
   1. The 2 lepton + missing Et final state: %$pp \to H\to W^+ W^- \to e^- \bar \nu_e \mu^+ \nu_\mu $ 
      * Signal 
         * 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]
         * 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]
      * Background 
         * 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]
         * 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]
   1. Top associated production %$pp \to t\bar tH$% with %$H \to b \bar b$% 
      * Signal + Background samples: 
         * 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]
         * 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]

=== MadGraph BlackBox Challenge ===

Three "black boxes" are given, in the form of event files in the LHC Olympics format and a series of selected plots:

   * 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]
   * 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]
   * 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]

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:

   * Model 1 : Extra Z (zp) : What its mass? Does it have Standard Model couplings to fermions?
   * Model 2 : Heavy Scalar (h): What its mass? Is it a SM Higgs?
   * Model 3 : Extra W (wp+ or wp-) : What its mass? Does it have Standard Model couplings to fermions?

Useful extra information:
   * In the plots %$H_T=\sum ||p_T^{vis}|| + E_T^{miss}$%.
   * 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-.
   * 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.
   * 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.

=== Monte Carlo's ===

For those interested in getting deeper into Monte Carlo techniques, here are some more exercises:

   * Write the simplest integration function based on the definition of average and error
   * Importance sampling via an analytic transformation
   * Von Neumann's rejection method : plain and improved
   * Phase space for 1 -> n particles
   * Vegas
   * Top decay : comparison among the various methods
   * qq -> tt production

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]
=== Animations ===
   * [http://madgraph.hep.uiuc.edu/Event/ Interactive Flash version] Note you may want to zoom in!
   * [http://madgraph.hep.uiuc.edu/Event/fast_collisionx6.avi Fast movie (.avi) of collision]
   * [http://madgraph.hep.uiuc.edu/Event/collision.mov Guided movie (.mov) of collision]
   * [http://www.thedailyshow.com/watch/thu-april-30-2009/large-hadron-collider John Ellis on Daily Show]

-- Main.TimStelzer - 2010-07-19