Presentation on theme: "Marianne BargiottiInternational Workshop on Heavy Quarkonium 2007 17-20 October 2007, DESY Hamburg MC and quarkonium physics studies for LHCb Marianne."— Presentation transcript:
Marianne BargiottiInternational Workshop on Heavy Quarkonium October 2007, DESY Hamburg MC and quarkonium physics studies for LHCb Marianne Bargiotti CERN
Marianne BargiottiInternational Workshop on Heavy Quarkonium October 2007, DESY Hamburg 2 Status of PYTHIA simulation: what has been done so far Brand new NRQCD processes introduced and tested in PYTHIA 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 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 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 , Jun 2007 M. BargiottiCERNV. VagnoniINFN, Bologna
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
Marianne BargiottiInternational Workshop on Heavy Quarkonium 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.