1. Marianne BargiottiInternational Workshop on Heavy Quarkonium 2007 17-20 October 2007, DESY Hamburg MC and quarkonium physics studies for LHCb Marianne Bargiotti CERN

2. Marianne BargiottiInternational Workshop on Heavy Quarkonium 2007 17-20 October 2007, DESY Hamburg 2 Status of PYTHIA simulation: what has been done so far  Brand new NRQCD processes introduced and tested in PYTHIA 6.324 onward: color octet mechanism introduced for:  S wave for cc and bb; color singlet new process:  implementation of g-g, q-g, q-q  c and  b  implementation of g-g, q-g, q-q channels for  c and  b  QCD perturbation theory breaks down at low p T values, confinement is not taken into account:  This is implemented in Pythia by the introduction of a p T min. cut-off, that can be an abrupt one, or an appropriately smoothed cut-off defined by a reweight of the cross section: together with a dampening of the strong coupling T. Sjostrand et al. Phys. Rev. D36:2019, 1987 JHEP 0403:053, 2004

3. 3 Status of PYTHIA simulation: what has been done so far  Most effective approach: Cross section smoothed reweighting  reweight event cross section by process type and kinematics of the hard scattering best p TMIN = 2.85 GeV  Issues : Colour Singlet cross section at high pT exceeds what one would expect, and this leads to a slight excess of the sum of the two contributions CSM+COM pT0 value slightly on the large side, one would hope e.g. for 2-2.5 GeV similarly to the value used in the Multiple Parton Interaction scheme in Pythia, which adopts the same concept and mechanism for dampening the divergent cross sections at low pT  No recent result on LHCb side: total lack of manpower on this side  Recent studies carried on by ATLAS/CMS (comparison among diff. generators: PYTHIA, COMPHEP and Alpgen) Total Color octet Color-singlet CTEQ6L |y|<0.6  Full description of the approach used in: Heavy quarkonia sector in PYTHIA 6.324: Tuning, validation and perspectives at LHC(b). M. Bargiotti (CERN), V. Vagnoni (INFN, Bologna). CERN-LHCB-2007-042, Jun 2007 M. BargiottiCERNV. VagnoniINFN, Bologna

4. 4 Quarkonium physics studies at LHCb  All decays are handled by EvtGen that handles spin correlations in the same way  No production polarization is taken into account at the moment.  Foreseen productions and investigations (depending on manpower availability) : production cross sections for J/  and Upsilon, as a function (or in a certain range) p T, y or x F. study on the polarization (spin alignment) as a function of the kinematics, and possibility to extract also a measurement for the b-cross section by looking for detached J/  vertices. Spectroscopy with  c states Possible investigations on reconstruction of  (3770) --> DD. Inital studies of quarkonium states will certainly focus on two muon final states. However, we should not forget the electron channels

5. Marianne BargiottiInternational Workshop on Heavy Quarkonium 2007 17-20 October 2007, DESY Hamburg 5 PYTHIA foreseen studies  Polarization production: test of polarization contribution from PYTHIA 6.4 onward  Y production testing   c,b contribution testing (explicitly useful for  c studies foreseen in near future)  Comparison of various MC tuning on cross section reweighting in order to extract a coherent value of p TMIN.