ALPGEN MC Generation at SPRACE

Introduction

Alpgen is a collection of codes (executables) for calculation of hard multiparton processes in hadronic collisions. It produces matrix element (ME) level events which are consecutively passed to a parton shower (PS) / hadronization code (like Pythia or HERWIG) for further event development. Using the MLM ME/PS matching procedure, one can combine the matrix element calculations with parton showers while avoiding double-counting. This allows for the best Monte Carlo prediction of multi-jet final states at this moment.

This page documents the usage of Alpgen at the São Paulo Regional Analysis Center - SPRACE, for large-scale productions of Monte Carlo events for the CMS Experiment.

Role of SPRACE

SPRACE is a Brazilian Tier 2 of the LHC Computing Grid. We are also a group dedicated to the generation of large numbers of parton-level Les Houches Accord events for the CMS Experiment. According to the proposed model, large-scale Alpgen Monte Carlo event productions at CMS are a 4-step process:

1. Generate events with standalone ALPGEN executable
2. Format shift to LHA events (AlpgenSource + LHEWriter). Document and upload to MCDB (http://mcdb.cern.ch).
3. Execution of CMSSW jobs at CERN, format shift to EDM files, publish them to DBS.
4. Deploy the files to the Tier 2 centers for further treatment .

At SPRACE we perform the first and second steps of this process.

Requesting a large scale Alpgen production at SPRACE.

If you're interested in requesting a large scale Alpgen production at SPRACE, you should contact ThiagoTomei, and discuss the details with him. In general, such a request consists of the following:

• The definition of the process to be run.
  • If it is a non-standard process (for instance, a W+jets production binned in W transverse momentum), the details on how to produce the corresponding executable.
  • Also, whether a grid is available for that particular process and if not, how is the grid goind to be produced.
• Size of the request (in some relevant metric: number of events, total CPU time, integrated luminosity of the sample).
• Priority of the request: in general, official CMS productions will have priority over individual CMS user requests. Actual priorities are decided in a case-by-case basis.
• More information on Alpgen usage: https://twiki.cern.ch/twiki/bin/view/CMS/SWGuideCMSAlpgen

Links

• AlpgenDevelopmentPage: internal documentation for the Alpgen team at SPRACE.
• AlpgenGridProductionPage: grids available for Alpgen productions at SPRACE.
• AlpgenValidationPage: how to validate the production output.
• AlpgenEventProductionPage: information about event productions performed at SPRACE.

-- ThiagoTomei - 03 Jun 2009