Quarkonia production at LHC Gobinda Majumder Preliminary FAMOS

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 • σ(J/ψ)*Br(μμ)=653 nb, χc. J =4. 69, 311, 129 nb • σ(ϒ(1 S))*Br(μμ)=27. 2 nb, χb. J =0. 50, 5. 52, 7. 47 nb

Momentum resolution of electron and muon J/ψ➔μμ J/ψ➔ee ΔPT (Ge. V) ϒ(1 S)➔μμ ϒ(1 S)➔ee Δθ (mrad) • Very poor efficiency and momentum resolution of electron for these low momentum tracks

Dimuon/Dielectron invariant mass from FAMOS J/ψ➔μμ J/ψ➔ee Mμμ (Ge. V) Mee (Ge. V) ϒ(1 S)➔ee ϒ(1 S)➔μμ • Muon track finding efficiency ~89%, looks to high, and also no background from minimum bias events • Electron track finding efficiency ~ 25%, very low and also poor mass resolution, might not help at all to improve significance/polarisation measurement of ϒ(1 S) or J/ψ

Expected events at CMS detector J/ψ➔μμ ϒ(1 S)➔μμ PT>7 Ge. V PT>7 PT>5 PT>6 Assumption • 100 pb─1 data • Trigger and muon isolation efficiency of this events = 50% PT>6 PT>5 PT > 7 Ge. V PT > 6 Ge. V PT > 5 Ge. V J/ψ→μμ 63 K 116 K 230 K ϒ(1 S)→μμ 15 K 28 K 62 K

Simulation of events with CMSSW • Events are generated with PYTHIA 6. 402 • Simulation + Digitisation + Reconstruction CMSSW_1_2_0 – – – Started with CMSSW_1_1_0 Many varieties of error/core dump/exception Move to CMSSW_1_2_0 Even known bug : Mixing module Unknown : Memomory leakage, but where ? Same scripts ended/exited with different number of events depending on initial seed – How CSA 06 has generated so many events ? • Muon selection : “global. Muons" • Electron selection : "si. Strip. Electron. To. Track. Associator“ • Beam background : – Without any minimum bias – With minimum bias event =3 and bunch [─1, 2] – With minimum bias event =3 and bunch [─5, 3]

Variables to select dilepton invariant mass : no minbias • Without any selection criteria

Selection criteria (not any optimisation) • • Number of degrees of freedom >20 (10) Normalised χ2 <5 (20) Transverse momentum of leptons >3 Ge. V Polar angle (virtually no criteria for the time being) Distance of closest approach of tracks (transverse) < 0. 1 cm Distance of closest approach of tracks (Longi) < 15 cm Closest distance between twp tracks (no cut, for the simulated signal events, it is very much correlated with PT • Prob (χ2, ndf) (not used)

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

Variables to select dilepton invariant mass : no minbias • With 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 resolution Without back/selec 108 Me. V With back w/o selec 107 Me. V • Tail in upper side • FAMOS result : resolution 65 Me. V W/o back with selec 110 Me. V With back/selec 109 Me. V

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

Dimuon invariant mass for sample H(190 Ge. V) →ZZ→μμμμ • Selection criteria are not optimised for these high momentum muon

Dimuon invariant mass for sample H(190 Ge. V) →ZZ→eeee • Even this high momentum electron has much poorer efficiency/resolution with respect to muon

Summary • Not much progress • Due to poor resolution and efficiency, dielectron channel is not promising !!!! Is it software problem or hardware ?

Onium production at LHC : ckin(3)=1 • σ(J/ψ)*Br(μμ)=26. 1 μb, χc. J =1. 05, 8. 2, 20. 5 μb • σ(ϒ(1 S))*Br(μμ)=180 nb, χb. J =7. 44, 13. 5, 104. 6 nb

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

Fast simulation with FAMOS • Generated only J/ψ➔μμ, J/ψ➔ee, ϒ(1 S)➔μμ, ϒ(1 S)➔ee events with ckin(3)=5 • Pre selected events with PT>4. 5 Ge. V and |η|<1. 3/2. 4 –at least one lepton in barrel region • Statistics = 10000 events for each type of MC events • Fast simulation with FAMOS_1_4_0 • Minimum bias events, <n>= 3. 5 • Look for momentum resolution of low momentum leptons • Look for dilepton invariant mass

Dielectron invariant mass (with [─1, 2] ) • Not possible at all with these low energy electrons

Motivation • Study of quarkonia productions provide important information on both pertubrative QCD and non pertubative QCD. • To make use of perturbative methods, separate the shortdistance/high momentum, perturbative effects from the longdistance/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 production • Creation of two on-shell heavy quarks (perturbative) and then bind them to make the meson(non perturbative) –factorisation • For bound state, quarks velocity inside the meson is very small -static approximation • The 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 gg→ 3 S 1 g diagrams within the CSM

J/ψ and ψ’ production anomaly at Tevatron J/ψ • Factor of 30 discrepancy with the production rate of J/ψ and ψ’ at CDF when compared with CSM • Try to explain the anomaly within CSM; gluon fragmentation into Pwave mesons, but fail to explain ψ’

Scattering at hadron collider How the outgoing quarks make colourless hadron, where gluon carries colour ? Basic concepts of color octet model QQ 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 production qq →ψg qg →ψq gg →ψg

Independent parameters in NRQCD Quarkonium production rate • Using heavy quark spin symmetry reduces the number of independent matrix element For S-wave charmonium multiplet consisting of J/ψ and ηc, there are four independent matrix elements, e. g. , Relative order in v (quark verlocity within the bound state, v 2≈0. 3 for charmonium and ≈0. 1 for bottomonium) are v 0, v 3, v 4 and v 4 Similarly for P-wave charmonium multiplet consisting of χc 0, χc 1, χc 2 and hc, there are only two independent parameters, e. g. The order in v relative to are both v 2

Explanation of CDF anomaly in COM J/ψ χc. J Ψ(2 S) ϒ(1 S)

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

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): PARP(141) 1. 16 PARP(142) 0. 0119 PARP(143) 0. 01 PARP(144) 0. 01 PARP(145) 0. 05 PARP(146) 9. 28 PARP(147) 0. 15 PARP(148) 0. 02 PARP(149) 0. 48 PARP(150) 0. 09 Large uncertainty in models and consequently these parameters, need to be tuned at LHC. ATLAS and LHC-B are ready to do that. 36