LHC Phenomenology with MadGraph
Copenhagen, 17-19 Nov 2010
Authors
- Fabio Maltoni (lecturer)
Lectures
Find the pdf of the 7 x 1.5 hours lecture:(available after lectures)
References
- QCD and Collider Physics by Keith Ellis, James Stirling, Bryan Webber (Cambridge Monographs, 1996).
- Perspectives on LHC physics, Ed. by G. Kane and A. Pierce.
MadGraph and Pheno Exercises
A summary of advanced QCD and pheno exercises can be found here.
Tutorial 1: Familiarize with MadGraph
- Logon to the 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.
- Kinematics at the LHC: refresh the kinematics of an hadron collider.
Tutorial 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):
- Jets : Di-jet kinematics and rates in pp collisions.
- 3 Jets : Energy distributions in 3-jet events.
- Drell-Yan : Study the rapidity asymmetry at the Tevatron.
- top production : $t \bar t$ production, Tevatron vs LHC.
- t' production : $t'$ production at the LHC.
Tutorial 3: The full simulation chain and advanced features
Try out the Analysis Tools:
- a Fortran-based package: MadAnalysis (Download it here)
Study what is known of a SM Higgs at the LHC:
- Find the best prediction for Higgs production at the LHC here.
- Find the Higgs branching ratios here.
Choose a channel and investigate signal and background:
- The 2 lepton + missing Et final state: $ pp \to H\to W+ W- \to e- \bar \nu_e \mu+ \nu_\mu $
- Signal
- Events: Parton Level Detector Level
- Plots: Parton Level Detector Level
- Background
- Events: Parton Level Detector Level
- Plots: Parton Level Detector Level
- Signal
- Top associated production $pp \to t\bar tH$ with $H \to b \bar b$
- Signal + Background samples:
- Events: Parton Level Detector Level
- Plots: Parton Level Detector Level
- Signal + Background samples:
Tutorial 4: The 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 : Events Plots: Parton level Detector level
- Box B : Events Plots: Parton level Detector level
- Box C : Events Plots: Parton level 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:
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: mc101.nb. Reference: Introduction to MC methods, by Stefan Weinzierl
Animations
- Interactive Flash version Note you may want to zoom in!
- Fast movie (.avi) of collision
- Guided movie (.mov) of collision
- John Ellis on Daily Show
-- Main.FabioMaltoni - 2010-11-14
Attachments (26)
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