Quarkonia production at LHC

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Quarkonia production at LHC. Gobinda Majumder. Preliminary FAMOS results on signal and CMSSW_1_2_0. India-CMS meeting 21-22 Jan 2007. Onium production at LHC : ckin(3)=5. (J/ )*Br( )=653 nb, cJ = 4.69, 311, 129 n b ( (1S) )*Br( )=27.2 nb, bJ = 0.50, 5.52, 7.47 n b. - PowerPoint PPT Presentation


  • Quarkonia production at LHC

    Preliminary FAMOS results on signal and CMSSW_1_2_0Gobinda MajumderIndia-CMS meeting 21-22 Jan 2007

  • Onium production at LHC : ckin(3)=5(J/)*Br()=653 nb, cJ =4.69, 311, 129 nb((1S))*Br()=27.2 nb, bJ =0.50, 5.52, 7.47 nb

  • Momentum resolution of electron and muon

    Very poor efficiency and momentum resolution of electron for these low momentum tracksPT (GeV)PT (GeV) (mrad) (mrad)J/J/ee(1S)(1S)ee

  • Dimuon/Dielectron invariant mass from FAMOSMuon track finding efficiency ~89%, looks to high, and also no background from minimum bias eventsElectron track finding efficiency ~ 25%, very low and also poor mass resolution, might not help at all to improve significance/polarisation measurement of (1S) or J/ J/eeJ/(1S)(1S)eeM (GeV)Mee (GeV)

  • Expected events at CMS detector 100 pb1 dataTrigger and muon isolation efficiency of this events = 50%AssumptionJ/(1S)PT>7 GeVPT>6PT>5PT>5PT>6PT>7

  • Simulation of events with CMSSWEvents are generated with PYTHIA6.402Simulation + Digitisation + Reconstruction CMSSW_1_2_0Started with CMSSW_1_1_0Many varieties of error/core dump/exception Move to CMSSW_1_2_0Even known bug : Mixing moduleUnknown : Memomory leakage, but where ? Same scripts ended/exited with different number of events depending on initial seedHow CSA06 has generated so many events ?Muon selection : globalMuons"Electron selection : "siStripElectronToTrackAssociatorBeam background : Without any minimum biasWith minimum bias event =3 and bunch [1, 2]With minimum bias event =3 and bunch [5, 3]

  • Variables to select dilepton invariant mass :no minbiasWithout any selection criteria

  • Selection criteria (not any optimisation)Number of degrees of freedom >20 (10)Normalised 2 3 GeVPolar angle (virtually no criteria for the time being)Distance of closest approach of tracks (transverse) < 0.1 cmDistance of closest approach of tracks (Longi) < 15 cmClosest distance between twp tracks (no cut, for the simulated signal events, it is very much correlated with PTProb (2, ndf) (not used)

  • Variables to select dilepton invariant mass :no minbiasWith the selection of all other criteria : Variables are correlated

  • Variables to select dilepton invariant mass :no minbiasWith the impose of criteria one by one

  • Variables to select dilepton invariant mass :[1, 2]Increases background as expected

  • Variables to select dilepton invariant mass :[5, 3]Background does not increase much (remember different statistics)

  • Dimuon invariant mass (without backgound)Removal of background tails for different selection criteria

  • Dimuon invariant mass (with [1,2])Extra background can be removed with selection criteria

  • Dimuon invariant mass (with [3,5])Not much difference with less number of branch crossings

  • Dimuon mass resolutionTail in upper sideFAMOS result : resolution 65 MeVWithout back/selec108 MeVWith back w/o selec107 MeVW/o back with selec110 MeVWith back/selec109 MeV

  • Dielectron invariant mass (without backgound)Both resolution as well as statistics has gone down drastically

  • Dimuon invariant mass for sample H(190 GeV) ZZSelection criteria are not optimised for these high momentum muon

  • Dimuon invariant mass for sample H(190 GeV) ZZeeeeEven this high momentum electron has much poorer efficiency/resolution with respect to muon

  • SummaryNot much progressDue to poor resolution and efficiency, dielectron channel is not promising !!!!!!!! Is it software problem or hardware ?

  • Onium production at LHC : ckin(3)=1(J/)*Br()=26.1 b, cJ =1.05, 8.2, 20.5 b((1S))*Br()=180 nb, bJ =7.44, 13.5, 104.6 nb

  • P-wave onium production at LHCMomentum spectrum is softer than muons from direct J/ and (1S) There are also J/ from the decay of B-hadron

  • Fast simulation with FAMOSGenerated only J/, J/ee, (1S), (1S)ee events with ckin(3)=5Pre selected events with PT>4.5 GeV and ||
  • Dielectron invariant mass (with [1,2] )Not possible at all with these low energy electrons

  • MotivationStudy of quarkonia productions provide important information on both pertubrative QCD and non pertubative QCD. To make use of perturbative methods, separate the short-distance/high momentum, perturbative effects from the long-distance/low momentum, nonperturbative effects a process which is known as factorisation Nonrelativistic QCD (NRQCD)perturbative calcultion, known well Non-perturbative calcultion, almost no theoretical calculation, except some lattice calculation Both ATLAS and LHC-B is looking for this signal, but there is no study in CMS

  • Charmonium family

  • Bottomonium family

  • Bottomonium family

  • Colour singlet model (CSM) of onium productionCreation of two on-shell heavy quarks (perturbative) and then bind them to make the meson(non perturbative) factorisationFor bound state, quarks velocity inside the meson is very small -static approximationThe colour and spin of the QQ pair do not change during the binding. As physical states are colourless, one requires the pair be produced in a colour-singlet state Colour Singlet Model (CSM) Leading order gg3S1g diagrams within the CSM

  • J/ and production anomaly at Tevatron Factor of 30 discrepancy with the production rate of J/ and at CDF when compared with CSMTry to explain the anomaly within CSM; gluon fragmentation into P-wave mesons, but fail to explainJ/

  • Scattering at hadron colliderHow the outgoing quarks make colourless hadron, where gluon carries colour ?

    Basic concepts of color octet modelQQ may have different quantum number, with the emission of soft gluon(s), coloured QQ converts to a neutral hadrons S-wave orthoquarkonium vector meson looks like

  • Colour octet quarkonium productionqq g qg q gg g

  • Independent parameters in NRQCDUsing heavy quark spin symmetry reduces the number of independent matrix elementQuarkonium production rate For S-wave charmonium multiplet consisting of J/ and c, there are four independent matrix elements,e.g.,Similarly for P-wave charmonium multiplet consisting of c0,c1,c2 and hc, there are only two independent parameters, e.g. Relative order in v (quark verlocity within the bound state, v20.3 for charmonium and 0.1 for bottomonium) are v0,v3,v4 and v4The order in v relative to are both v2

  • Explanation of CDF anomaly in COMJ/(2S)cJ(1S)

  • Polarisation, double charmonium ?Polarisation results are not conclusive, need more studyDouble charmonium production at B-factories is too large to explain in COM(2S)

  • New parametes : the NRQCD matrix elements in PYTHIA* The rates for these new processes are regulated by 10 NEW NRQCD matrix elements values (their default values are set to one in the current release, and need tuning):Large uncertainty in models and consequently these parameters, need to be tuned at LHC. ATLAS and LHC-B are ready to do that.