Quarkonia production at LHC

Preliminary FAMOS results on signal and CMSSW_1_2_0

Gobinda Majumder

India-CMS meeting 21-22 Jan 2007

Onium production at LHC : ckin(3)=5

• σ(J/ψ)*Br(μμ)=653 nb, χcJ =4.69, 311, 129 nb• σ(ϒ(1S))*Br(μμ)=27.2 nb, χbJ =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 tracks

ΔPT (GeV) ΔPT (GeV)

Δθ (mrad) Δθ (mrad)

J/ψ➔μμ J/ψ➔ee

ϒ(1S)➔μμ ϒ(1S)➔e

e

J/ψ➔ee

Dimuon/Dielectron invariant mass from FAMOS

• 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(1S) or J/ψ

J/ψ➔μμ

ϒ(1S)➔μμ

ϒ(1S)➔ee

Mμμ (GeV) Mee (GeV)

Expected events at CMS detector

• 100 pb─1 data

• Trigger and muon isolation efficiency of this events = 50%

PT > 7 GeV PT > 6 GeV PT > 5 GeV

J/ψ→μμ 63K 116K 230K

ϒ(1S)→μμ

15K 28K 62K

Assumption

J/ψ➔μμ

ϒ(1S)➔μμ

PT>7 GeV PT>6 PT>5

PT>5PT>6PT>7

Simulation of events with CMSSW• Events are generated with PYTHIA6.402

• 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 CSA06 has generated so many events ?

• Muon selection : “globalMuons"

• Electron selection : "siStripElectronToTrackAssociator“

• 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 GeV

• 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

• Tail in upper side

• FAMOS result : resolution 65 MeV

Without back/selec

108 MeV

With back w/o selec

107 MeV

W/o back with selec

110 MeV

With back/selec

109 MeV

Dielectron invariant mass (without backgound)

• Both resolution as well as statistics has gone down drastically

Dimuon invariant mass for sample H(190 GeV) →ZZ→μμμμ

• Selection criteria are not optimised for these high momentum muon

Dimuon invariant mass for sample H(190 GeV) →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, χcJ =1.05, 8.2, 20.5 μb• σ(ϒ(1S))*Br(μμ)=180 nb, χbJ =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(1S) • There are also J/ψ from the decay of B-hadron

Fast simulation with FAMOS

• Generated only J/ψ➔μμ, J/ψ➔ee, ϒ(1S)➔μμ, ϒ(1S)➔ee events with ckin(3)=5

• Pre selected events with PT>4.5 GeV 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 short-distance/high momentum, perturbative effects from the long-distance/low momentum, nonperturbative effects –a process which is known as “factorisation” –Nonrelativistic QCD (NRQCD)

)()(][ Hnn n OH

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→3S1g diagrams

within the CSM

J/ψ and ψ’ production anomaly at Tevatron

• 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 P-wave mesons, but fail to explain

J/ψψ’

Scattering at hadron colliderQQ

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

• Using heavy quark spin symmetry reduces the number of independent matrix element

)()(][ Hnn n OH Quarkonium production rate

For S-wave charmonium multiplet consisting of J/ψ and ηc, there are four independent matrix elements,e.g.,

)(,)(,)(,)( 03/

813/

801/

813/

1 POSOSOSO JJJJ

Similarly for P-wave charmonium multiplet consisting of

χc0,χc1,χc2 and hc, there are only two independent parameters, e.g. )()( 1

310

31

00 SOandPO cc

Relative order in v (quark verlocity within the bound state, v2≈0.3 for charmonium and ≈0.1 for bottomonium) are v0,v3,v4 and v4

The order in v relative to are both v2 )( 13/

1 SO J

Explanation of CDF anomaly in COM

J/ψ Ψ(2S)

χcJ ϒ(1S)

Polarisation, double charmonium ?

• Polarisation results are not conclusive, need more study

• Double charmonium production at B-factories is too large to explain in COM

Ψ(2S)

36

New parametes : the NRQCD matrix elements in PYTHIA

PARP(150)

PARP(149)

PARP(148)

PARP(147)

PARP(146)

PARP(145)

PARP(144)

PARP(143)

PARP(142)

PARP(141)

0.09

0.48

0.02

0.15

9.28

0.05

0.01

0.01

0.0119

1.16

/ 3 (1)1[ ]JO S

/ 3 (8)1[ ]JO S

/ 1 (8)0[ ]JO S

/ 3 (8) 20[ ] /J

cO P m

0 3 (1) 20[ ] /c

cO P m

3 (1)1[ ]O S

3 (8)1[ ]O S

1 (8)0[ ]O S

3 (8) 20[ ] / bO P m

0 3 (1) 20[ ] /b

bO P m

The rates for these new processes are regulated by 10 10 NEW NRQCDNEW 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.