1. Gauss: Generator Status Patrick Robbe, LAL Orsay, 6 Oct 2009

2. 2 Generator Status MC09 production running correctly with:  Pythia 6.4 (most recent FORTRAN version)‏  New EvtGen, after merging LHCb+BaBar+Tevatron last developments Spill-over generation in Gauss (not used for MC09) has been implemented:  Cannot be used to generate spill-over for special event types (B c, Z 0, W, Higgs,...)‏

3. 3 Latest Developments B c generation has been updated to MC09 Gauss versions,  and many small problems fixed (PDF initialization,...) by Jibo He, and can now be used since Gauss v34r5. New models in LHCb EvtGen for B -> X ll generation (including B s )‏  Implemented by Nikolai Nikitin, available in Gauss v34r4 SHERPA integration ongoing (Dortmund group):  C++ generator, alternative to both Pythia (production) and EvtGen (decay). Main work on decay part.  Can already be used as decay tool, with limitations: Cannot handle correctly decay of broad hadrons produced by Pythia Cannot generate CP violation in signal events (but can generate in inclusive b, opposite to EvtGen)‏

4. 4 Generator Problems Problems have appeared when generating signal event types:  B 0 → K*e + e - /B 0 → K*  +  - : bug introduced in BaBar which propagated to LHCb, fixed in Gauss v34r4. Future EvtGen maintainance ? (package will be less and less maintained and tested by BaBar)‏  Some decay files are obsolete or not correctly tested and crash in production. A quick test of the decay file should be performed by its author before being released: How to test a decay file: http://lhcb-release-area.web.cern.ch/LHCb-release- area/DOC/gauss/generator/evtgen.php List of old or untested decay files: http://lhcb-release-area.web.cern.ch/LHCb- release-area/DOC/decfiles/releases/latest/table_evttype.php  CP violation: It has been showed that CP violation generation does not work with new EvtGen. No correction yet.

5. 5 Useful Links MC09 parameters:  https://twiki.cern.ch/twiki/bin/view/LHCb/SettingsMc09 MC09 generator efficiencies:  http://lhcb-release-area.web.cern.ch/LHCb-release- area/DOC/STATISTICS/MC09STAT/Generation_MC09-b5TeV-md100.html LHCb/EvtGen documentation:  http://lhcb-release-area.web.cern.ch/LHCb-release-area/DOC/gauss/generator/evtgen.php List of event types and their documentation:  http://lhcb-release-area.web.cern.ch/LHCb-release-area/DOC/decfiles/releases/latest/table_evttype.php Everything is accessible from the Gauss web- page:  http://lhcb-release-area.web.cern.ch/LHCb-release-area/DOC/gauss/

6. 6 Conclusion: Future Work CP violation generation correction Need to move to C++ Pythia: Pythia 8 Need to think about maintainance of EvtGen (or move to Sherpa)‏ Tuning of generators with first data:  Work prepared in Flavour Working Group  Need to be in contact with generator authors (Pythia,...)‏