Collider Event Generation
NumS-HEP 2011 school, NCTU, Taiwan, 17-23 Jan 2011
Authors
- Johan Alwall (lecturer)
Lectures
Find the pdf of the 3 x 1.5 hours 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.
- Pythia 6 Physics and Manual (excellent introduction to event generation, parton showers and hadronization).
Basic exercises 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 (in SM and HEFT)
- uu~>tt~bb~
- Subprocess identification. List all subprocesses contributing to:
- pp>l+vljj
- 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.
Basic exercises 2: Calculate cross sections and generate events
- Generate events for a few selected processes (work in groups, pick one each), for Tevatron and LHC energies. Does the cross section scale as you expect?
- Compare cross sections with the processes of your neighbors. Do they differ as you would expect?
- Look at the generated plots. Are the distributions as you would expect? Discuss with your neighbors.
Example processes:
- ttbar production: pp > tt~, QED=0
- W production: pp > l+vl
- Z/gamma* production: pp > e+e-
- g g > (H > e+ ve mu- vm~) (in HEFT model)
- p p > (W+>e+ ve) (W- > mu- vm~) (important background to previous process)
Advanced exercises 1: The full simulation chain and advanced features
Try out the Analysis Tools:
- a Fortran-based package: MadAnalysis (Download it here)
- a Root-based package: ExRootAnalysis (Download it here)
- a Mathematica-based package: Chameleon
Study SM Higgs production at the LHC. Choose a channel and investigate signal and background, using either of the packages above:
- The 2 lepton + missing Et final state: $ pp \to H\to W+ W- \to e- \bar \nu_e \mu+ \nu_\mu $
-
- Signal
- Signal
Detector Level |
Detector Level |
- Background
Detector Level |
Detector Level |
- Top associated production $pp \to t\bar tH$ with $H \to b \bar b$
- Signal + Background samples:
- Signal + Background samples:
Detector Level |
Detector Level |
Advanced exercises 2: Implementation of a new model in MadGraph or FeynRules + MadGraph
Note that for these exercises you need to download the MadGraph/MadEvent package (or MadGraph 5 package) and work locally. You need a Fortran compiler (and for MadGraph 5, Python v. 2.6 or 2.7).
For FeynRules download and information, see the FeynRules wiki
- Implement a (part of a) Standard Model extension into MadGraph, specific for studying a given process. Generate events, study relevant distributions.
- Determine most relevant Standard Model backgrounds with identical final states (“non-reducible”). If not too complicated, generate backgrounds with cuts determined from signal distributions.
- Which other (“reducible”) backgrounds might be important?
- Can the signal be seen at Tevatron? At the LHC?
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.JohanAlwall - 2011-01-17
Last modified
12 years ago
Last modified on Apr 19, 2012, 9:32:10 AM
Attachments (13)
- hww-signal.lhe.gz (12.3 MB ) - added by 12 years ago.
- hww-signal-lhe.pdf (63.6 KB ) - added by 12 years ago.
- hww-background.lhe.gz (11.5 MB ) - added by 12 years ago.
- hww-background-lhe.pdf (63.5 KB ) - added by 12 years ago.
- ttbb.lhe.gz (1.4 MB ) - added by 12 years ago.
- ttbb-lhe.pdf (109.2 KB ) - added by 12 years ago.
- NumS-HEP_lectures.pdf (6.9 MB ) - added by 12 years ago.
- hww-signal.lhco.gz (3.1 MB ) - added by 12 years ago.
- hww-signal-lhco.pdf (442.8 KB ) - added by 12 years ago.
- hww-background.lhco.gz (2.6 MB ) - added by 12 years ago.
- hww-background-lhco.pdf (445.5 KB ) - added by 12 years ago.
- ttbb.lhco.gz (1.5 MB ) - added by 12 years ago.
- ttbb-lhco.pdf (363.9 KB ) - added by 12 years ago.
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