1

Zhangbu Xu (for the STAR Collaboration)

Brookhaven National Laboratory

High-pT J/atSTAR

Outline:

• Introduction

• J/ yields and suppression

• J/-h correlation

• Outlook (+MTD)

Quarkonia in sQGP

• Color screening effect 1)

• Recombination 2)

• Gluon energy loss 3)

• Heavy quark energy loss 3)

• Decay feed-down

• (comover, cold matter effect) at (hadronic phase, initial stage)

2

1) T. Matsui and H. Satz, Phys. Lett. B178, 416 (1986)2) R. L. Thews and M. L. Mangano, Phys. Rev. C73, 014904 (2006)3) M. B. Johnson et al., Phys. Rev. Lett. 86, 4483 (2001) and R. Baier et al., Ann. Rev. Nucl. Part. Sci. 50, 37 (2000)

How do the quarkonium behave in the presence of sQGP?

High pT J/ in heavy ion collisions

3

J/H. Satz, Nucl. Phys. A (783):249-260(2007)

J/ suppression at low pT could befrom suppressed excited states (’, c)F. Karsch, D. Kharzeev and H. Satz, PLB 637, 75 (2006)

High pT direct J/suppression related to hot wind dissociation?

Hot wind dissociation

H. Liu, K. Rajagopal and U.A. WiedemannPRL 98, 182301(2007) and hep-ph/0607062

2-component approachPredicted decrease RAA

X. Zhao and R. Rapp, hep-ph/07122407

Color singlet model predicted an increase RAA

(formed outside of medium)K. Farsch and R. Petronzio, PLB 193(1987), 105 J.P. Blaizot and J.Y. Ollitrault, PLB 199(1987),499

T. Gunji, QM08

The STAR Detector

Zebo Tang, USTC/BNL 4

MagnetMagnet

CoilsCoils

Central Central TriggerTriggerBarrel Barrel (CTB)(CTB)

ZCalZCal

Time Time Projection Projection

ChamberChamber(TPC)(TPC)

Year 2000Year 2000

Barrel EM Cal Barrel EM Cal (BEMC)(BEMC)

Silicon Vertex Silicon Vertex Tracker (SVT)Tracker (SVT)Silicon Strip Silicon Strip Detector (SSD)Detector (SSD)

FTPCFTPCEndcap EM CalEndcap EM CalFPDFPD

TOFp, TOFrTOFp, TOFr

PMDPMD

Year 2001+Year 2001+

Large acceptance: 2 coverage at mid-rapidity

Future upgrade: Time of Flight, DAQ1000, Heavy Flavor Tracker, Muon Telescope DetectorFuture upgrade: Time of Flight, DAQ1000, Heavy Flavor Tracker, Muon Telescope Detector

5

Low pT J/ in p+p at 200 GeV

J/ trigger 0 < pT < 5.5 GeV/c

MC describes position and width

p+p 200 GeV

STAR has J/ capabilities at low pT

Mass and width consistent with MC simulation, low mass tail from electron bremsstrahlung

Integrated p+p luminosity at 200 GeV: 0.4 (pb)-1

High pT J/ in p+p at 200 GeV

6

J/ pT

J/ pT

EMC+TPC electrons:1, pT>2.5 GeV/c

TPC only electrons:1, pT>1.2 GeV/c

EMC+TPC electrons:1, pT>4.0 GeV/c

TPC only electrons:1, pT>1.2 GeV/c

No background at pT>5GeV/c

Reach higher pT (~14GeV/c)

p+p 2005

p+p 2006

(S+B)/B: 24/2

(S+B)/B: 54/14

EMC trigger

3 pb-1

11 pb-1

7

J/ spectra in p+p at 200 GeV

• Significantly extend pT range of previous measurements in p+p at RHIC to 14 GeV/c

• Agreement of charm measurements between STAR and PHENIX

• Consistent with Color Evaporation calculations (R. Vogt, Private communication)

J/ in Cu+Cu

•Signal with good S/B ratio •pT range overlaps with p+p data•Luminosity: 0.9 nb-1

Nuclear modification factor RAA

9

• Double the pT range to 10GeV/c

• Consistent with no suppression at high pT:

RAA(pT>5 GeV/c) = 0.9±0.2 2 above low-pT data

• Indicates RAA increase from low pT to high pT

• Doesn’t agree with AdS/CFT prediction

• Formed out of medium?Affect by heavy quark/gluon energy loss

• Decay from other particles? 2-component Approach predicted slightly increase RAA after more consideration X. Zhao, WWND2008

RAA Comparison to NA60

200NNs GeV

10

RHIC: Cu+Cu, consistent with no suppression at pT > 5 GeV

17.3NNs GeV SPS: In+In, , consistent with no suppression at pT > 1.8 GeV

CroninpAppThermal fit

R. Arnaldi (NA60) QM08

Important to understand production mechanism

Quarkonium production mechanism Color singlet model (CSM) 1) pQCD Color octet model (COM) 2) NRQCD Color evaporation model (CEM) 3)

…

• Gluon fusion

• Heavy quark fragmentation 4)

• Gluon fragmentation 5)

• Decay feed-down

• …

11

1) R. Baier et al., PLB 102, 364 (1981)2) M. Kramer, Progress in Particle and Nuclear Physics 47, 141 (2001)3) H. Fritzsch, PLB 67, 217 (1977)4) Cong-Feng Qiao, hep-ph/02022275) K. Hagiwara et al., hep-ph/0705.0803

NRQCD

What’s the production mechanism at RHIC energy?

CSM with kt-factorization

12

CSM can also describe the data with some improvement likethe kt-factorization approach

PHENIX, PRL 92, 05180 (2004)

S.P. Baranov and A. SzczurekarXiv:0710.1792

d/d

pT [

nb/(

GeV

/c)]

p T (GeV/c)

Color singletLHC 14 TeV

Tevatron 1.96 TeV LO NLO

PRL98, 252002(2007)

xT scaling

13

n is related to thenumber of point-likeconstituents taking anactive role in theinteraction

n=8: diquark scatteringn=4: QED-like

scattering

xT scaling: and proton: n=6.5±0.8 PLB 637, 161(2006) J/: n=5.6±0.2 J/ production: closer to 22 scattering

(B J/)/(inclusive J/)

14

1) Generated B spectrum is from pQCD

M. Cacciari, P. Nason and R. Vogt

PRL 95(2005),122001

2) Decay BJ/, kinematics and branch ratio are from CLEO measurements

CLEO collaboration

PRL 89(2002),282001

• BJ/ contributes significantly to the inclusive J/ yields at high pT (>5 GeV/c) Assuming B production from pQCD (no experimental B spectra at RHIC yet)• Can be used to constrain B production

More J/ production puzzles

c

0D

15

Belle, PRL 89, 142001(2002)

e+e-, 10.6 GeV

0.82 ±0.15 ± 0.14 from new analysis.

While CEM predict 0.049 D. Kang, et al., PRD 71, 094019 and hep-ph/0412381

T. Uglov, EPS 2003

What happens?: In p+p collisions;At higher energy (200 GeV)

(e+e- J/ +cc)/(e+e- J/ + X) = 0.59+0.15-0.13 ±0.12

NRQCD predict ~0.1 K. Liu and Z. He, PRD 68, 031501 (2003)

B.L. Loffe and D.E. KharzeevPRD 69, 014016 (2004)

0c(2 )c S *D

c

J/-hadron correlation

RBRC Workshop, BNL, April 23-25, 2008

16

(S+B)/B: 54/14Heavy quark fragmentation

Near side correlation

Good S/B ratio makes this measurement possible

Disentangle contributions via Correlations

17

• J/-hadron correlation can also shed light on different source contribution to J/ production

• May be used to distinct CSM and COM

1)

no near side correlation

2)

strong near side correlation

g g g /J

g g b b hadron

B X /J X

PLB 200, 380(1988) and PLB 256,112(1991)

J/hadron correlation in p+p

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PRL 95,152301(2005)

h-h correlation• No significant near side J/-hadron azimuthal angle correlation

• Constrain B meson’s contribution to J/ yield

• Hints of CSM?

Yields in near/away side

19

Associated hadron spectra with leading J/: • Away side: Consistent with leading charged hadron correlation measurement (h-h) away-side from gluon or light quark fragmentation • Near side: Consistent with no associated hadron production BJ/ not a dominant contributor to inclusive J/ constrain J/ production mechanism

Constrain Bottom yields

• pQCD predicts significant BJ/ • Correlations shows low B contribution• can used to further constrain B yields• PYTHIA productions all show strong near-side correlation higher order production mechanism?

21

Future dramatic improvement of J / at low pT

EMC+TOF (large acceptance):• J / production • Different states predicted to melt at

different T in color medium• Charmonia(J/), bottonia ()

Quarkonium dissociation temperatures – Digal, Karsch, Satz

pT (e)>1.5 GeV/c

PHENIX Acceptance: ||<0.35,=2*/2 STAR TOF-Upgrade Acceptance: ||<0.9,=2*

J/ yields from 109 minbias Au+Au events: 43.8x10-9/0.040x109*292*0.5*1.8*0.5= 144,0000.3% v2 errorJ/pp N Nbin y RAA

dE/dx after TOF cut

High luminosity for Υ & high-pT J/

RHIC II + DAQ1000:Time-Of-Flight:

Electron identification Enhance statistics

Longer term: Quarkonia in STARHeavy Flavor Tracker:

Muon Telescope Detector:

e+e- rejection

Topologically reconstructJ/ from B decay

Rejection power: ~16

+-

simulationMuon identification

24

A novel and compact muon telescope detector for QCDLab

A large area of muon telescope detector (MTD) at mid-rapidity, allows for the detection of

• di-muon pairs from QGP thermal radiation, quarkonia, light vector mesons, possible correlations of quarks and gluons as resonances in QGP, and Drell-Yan production • single muons from their semi- leptonic decays of heavy flavor hadrons• advantages over electrons: no conversion, much less Dalitz decay contribution, less affected by radiative losses in the detector materials

+-

BNL LDRD 07—007 project

25

Concept of Design

A pseudo detector with scintillator covering the whole iron bars and left the gaps in-between uncovered.

1. muon efficiency: 35-45%, pion efficiency: 0.5-1%2. muon-to-pion enhancement factor: 50-1003. muon-to-hadron enhancement factor: 100-1000 including track

matching, tof and dE/dx4. dimuon trigger enhancement factor from online trigger: 10-50

Detection efficiency

pT (GeV)

pionmuon

This together with DAQ1000 will greatly enhance our capability of J/ and other dilepton program in RHIC II and future QCD Lab

Cosmic Ray Results: Long-Strip Multi-gap Resistive Plate Chamber Technology

Long MRPC Technology with double-end readout

HV: 6.3 KV

gas mixture: 95% Freon + 5% isobutane

time resolution: ~60 ps

spatial resolution: ~1cm

efficiency: >95%

950 mm

25

6

mm

25

m

m

Y. Sun et al., nucl-ex/0805.2459

27

HV: 6.3 KVgas mixture: 95% Freon + 5%

isobutanetime resolution: ~60-70 ps

spatial resolution: ~0.6-1cmefficiency: >95%

consistent with cosmic test results

Tsinghua module as

trigger

Scintillator as trigger

USTCY. Sun et al., nucl-ex/0805.2459

Fermi Lab Beam Test Results (T963 May 2-15 2007)

28

STAR-MTD in Year 2007

• iron bars as hadron absorber; two scintillator trays as our trigger

• 403 cm away from TPC center, ||<0.25

• gas: 95% Freon and 5% iso-butane; HV: 6.3 KV

• MTD Triggered events: 380 K Au+Au events were taken 1.7 M d+Au and 700 K p+p events taken in run 8

29

Performance at STAR

• MTD hits: matched with real high pT tracks

• z distribution has two components: narrow (muon) and broad (hadron) ones

• spatial resolution (narrow Gaussian) is ~10 cm at pT>2 GeV; hadron rejection: 200-300

• time resolution: 300 ps Improve our electronics with full scale detector

STAR Preliminary

pT>2 GeV/c

STAR Preliminary

30

Compared to Simulation

from data: pT>2 GeV/c, (z) of muon: ~10 cm

from simulation: pT=2.5 GeV/c, (z) of muon: ~9 cm

Data and simulation show consistent results

pT (

GeV

/c)

z (cm)

muons pions muons

Are they prompt muons?

MTD hit distribution

dE/dx (

Time of flight ()

Ks-

Kaon dE/dx

n<-1 n>0

n>0pT>2 GeV/c

STAR Preliminary

pT>2 GeV/c

Nu XuRHIC Science and Technology

Review, July 7-9, 200832/30

A complete MTD at STAR

MRPC ToF MRPC ToF barrelbarrelReady for run 10Ready for run 10

RPSD

PMD

FPD

FMS

EMC barrel

EMC End Cap

DAQ1000DAQ1000Ready for run 9 FGT

Complete

Ongoing

MTD

R&DHFT

TPC

• To install another tray with TOF electronics in run9• Collaborators for a proposal of full scale detector:

56.6% in azimuth, |eta|<0.88; current tray design: 360 modules, 2160 read-out strips, 4320 channels. (TOF: 23 K readout channels).

Summary (J/)

33

• J/ spectra in 200 GeV p+p collisions at STAR1. Extend the pT range up to ~14 GeV/c 2. Spectra can be described by CEM and CSM. 3. High pT J/ follows xT scaling with n=5.64. Spectra at high pT can be used to constrain B production

• Jhadron azimuthal correlation in p+p

1. no significant near side correlation Expect strong near-side correlation from BJ/+X Can be used to constrain J/ production mechanism

2. Away-side spectra consistent with h-h correlation indicates gluon or light quark fragmentation

• J/RAA from 200 GeV Cu+Cu collisions at STAR1. Extend RAA from pT = 5 GeV/c to 10 GeV/c2. Indication of RAA increasing at high pT

Future

34

J/ results from Run 7 Au+Au, data is still under production

Upsilon RAA

Run 8 (d+Au) just finished, Cold Nuclear Modification

Run9—10, Au+Au and p+p runs with TOF and DAQ1000

Longer term: HFT, MTD

Backup slides

35

36

Datasets

p+p data sample: 1. EMC triggered events in year 2005 ET>3.5 GeV Integrated luminosity: 3 (pb)-1

2. EMC triggered events in year 2006 ET>5.4 GeV Integrated luminosity: 11 (pb)-1

Cu+Cu data sample: 1. EMC triggered events in year 2005 ET>3.75 GeV Integrated luminosity: 0.9 (nb)-1

pp-equivalent: 3 (pb)-1

High-pT J/p+p data sample:• 1. J/ψ triggered events in year 2006

• Integrated luminosity: 377 (nb)-1

• 2. Υ triggered events in year 2006

• Integrated luminosity: 9(pb)-1

Au+Au data sample:• 1. Υ triggered events in year 2007

Integrated luminosity: 300(μb)-1

pp-equivalent: 12(pb)-1

Triggered data

06/17/2008 Lijuan Ruan (UC Davis Collboration Meeting) 37

Muon Identification: dE/dx Effect

STAR Preliminary

n<-1

STAR Preliminary

n>0

• the narrow Gaussian distribution: dominated by muons

STAR Preliminary STAR Preliminary

|z|<20

06/17/2008Lijuan Ruan (UC Davis Collboration

Meeting)38

How do I know dE/dx is right?

dE/dx: by selecting pions from KS daughternsigmapion for pion: -1.16 (mean), 1.14 (sigma)

06/17/2008 Lijuan Ruan (UC Davis Collboration Meeting) 39

• the narrow Gaussian distribution: dominated by muons

Muon Identification: Cut on High Velocity STAR Preliminary

STAR Preliminary

STAR Preliminary

STAR Preliminary

1/trackhits- 1/rawhits >0

n>0

STAR Preliminary

06/17/2008Lijuan Ruan (UC Davis Collboration

Meeting)40

Muons from Pion Decay?

Primary tracksOther sector: 4.65e05 pT> 2 GeV/c tracks, 2236 KS reconstructed.

MTD matched tracks: 2619 tracks, 3.35.8 KS obsverd. If all muons are from pion decay, 13 KS expected.

Consistent with no secondary muon contribution to narrow Gaussian from pion decay.

06/17/2008Lijuan Ruan (UC Davis Collboration

Meeting)41

Muons from Kaon Decay?

Left plot: no dE/dx cut Right plot: -5<n<-2.6, Pion(-1.2) Muon(-0.6) Kaon(-2.6), then Muon: 4.8%,Kaon: 48%. I observed 99-1624*4.8%=22 muons.

Muons from kaon decay: 22/48%/1624=2.8%.

Secondary muons contribution to narrow Gaussian is small from kaon decay.

pT>2 GeV/c

STAR Preliminary