Version 5 (modified by md987, 8 years ago) (diff)

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## Collider Event Generation

### Authors

• Johan Alwall (lecturer)

### Lectures

Find the pdf of the 3 x 1.5 hours lectures:

### 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:

Study SM Higgs production at the LHC. Choose a channel and investigate signal and background, using either of the packages above:

1. The 2 lepton + missing Et final state:
• Signal
Events: Parton Level
Plots: Parton Level
• Background
Events: Parton Level
Plots: Parton Level
1. Top associated production with
• Signal + Background samples:
Events: attachment:ttbb.lhe.gz Parton Level]
Plots: Parton 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 (&ldquo;non-reducible&rdquo;). If not too complicated, generate backgrounds with cuts determined from signal distributions.
• Which other (&ldquo;reducible&rdquo;) backgrounds might be important?
• Can the signal be seen at Tevatron? At the LHC?

#### Animations

-- Main.JohanAlwall - 2011-01-17