# Presentation: 375944

## J/ production in Cu+Cu and Au+Au collisions at RHIC-PHENIX

- <date/time>

- J/ production in Cu+Cu and Au+Au collisions at RHIC-PHENIX

- Susumu X. Oda for the PHENIX collaboration
- CNS, University of Tokyo
- February 9 (Sat.), 2008, Jaipur, India
- XVIII-2, Quark Matter 2008

**1/22**

## Physics motivation 

- Physics motivation

**2/22**

- J/ is one of the most important probes for quark gluon plasma study.
- J/ will dissociate in QGP by Debye color screening.
- Heavy quarks are created in initial hard collisions.
- Mainly gluon fusion at RHIC energy
- Competing effects
- Cold nuclear matter effects
- Nuclear breakup, shadowing, CGC
- Feed-downs from c, ’ and bottom
- Sequential dissociation
- Regeneration from uncorrelated charm quarks
- Need to experimentally disentangle these effects.

- H. Satz, J. Phys. G 32, R25 (2006)

**Notes:**
Physics motivation of J/psi measurement in heavy ion collisions is the most important probe for QGP study.
Due to Debye color screening, J/psi will dissociate in the QGP. 
At RHIC energy, heavy quarks are created in initial hard collisions, mainly gluon fusion.
However, there are competing effects, such as cold nuclear matter effects, feed down from excited charmonia and bottom quarks. 
Regeneration of J/psi from uncorrelated charm and anti-charm quarks is also important.
So, we need to experimentally disentangle these effects.

## PHENIX detector

- Timing, charged particle multiplicity
- BBC
- Spectator neutron
- ZDC

**Forward rapidity **(1.2<|y|<2.2, +- pair)
- Tracking
- MuTr (MWPC)
- PID
- MuID (drift tube, absorber)

**Midrapidity**** **
**	**(|y|<0.35, e+e- pair, photon, hadron)
- Tracking
- DC, PC
- PID
- RICH, EMCal

**3/22**

**Notes:**
This is the experimental setup. 
The PHENIX detector is located at the RHIC collider in BNL. 
We measure collision vertex by beam beam counters which measure charged particle multiplicity. 
Zero degree calorimeters detect spectator neutrons. 
We combine information of BBC and ZDC, and determine collision centrality. 
J/psi is measured via electron pair at mid rapidity and muon pair at forward rapidity. 
Electron is tracked by drift chambers and pad chambers and is identified by ring image Cherenkov counters and electromagnetic calorimeters.
Muon trackers measure muon momentum and muon identifiers perform identification. 

## What PHENIX has done on quarkonia from QM06

- Final results
- J/ in Cu+Cu collisions
- This talk
- arXiv:0801.0220 [nucl-ex]
- Updated J/ in d+Au collisions
- M. Wysocki’s talk (VI-2, Tuesday, finished)
- arXiv:0711.3917 [nucl-ex], to be published in Phys. Rev. C
- Preliminary results
-  c in p+p collisions
- This talk
-  ’ in p+p collisions
- M. Donadelli’s poster (P127)
- b quark in p+p collisions
- Y. Morino’s talk (XIV-5, Friday, finished)
- J/ elliptic flow in Au+Au collisions
- C. Silvestre’s talk (XVIII-4, this session)
- C.L. Silva’s poster (P85)
- Ongoing analyses
-  ’ and  in d+Au and Cu+Cu collisions
- H. Liu’s poster (P98)

**4/22**

## Feed-downs into J/ are important to understand the J/ suppression 

- The fractions of J/ sources from e.g. R. Vogt, Nucl. Phys. A700, 539 (2002) are
- Direct production : ~58%
- Decays from c0, c1, c2 : ~30%
- Decays from ’ : ~12%
- Decays from b quarks : neglected
- PHENIX currently does not have vertex detectors
- Inclusive J/ measurement in p+p collisions by PHENIX in Run-5 in 2005
- BR(J/l+l-)(J/)=178 ± 3(stat) ± 53(syst) ± 18(norm) nb
- Phys. Rev. Lett. 98, 232002 (2007), arXiv:hep-ex/0611020
- PHENIX separately measured these feed-down contributions in p+p collisions at midrapidity (|y|<0.35).

**5/22**

## cJ/+e+e-(p+p 200GeV, Run-5&6)

- cJ/+e+e-(p+p 200GeV, Run-5&6)

- PDG 2007 values
- BR(c0J/+)=1.32  0.11%
- neglected
- BR(c1J/+)=35.9 ± 1.9%
- BR(c2J/+)=20.3  1.0%

**6/22**

## ’e+e-  (p+p 200GeV, Run-6)

- M. Donadelli’s poster (P127)

- ’e+e-  (p+p 200GeV, Run-6)

**7/22**

- PHENIX preliminary
- BR(’e+e-)(’)/BR(J/e+e-)(J/)
- 	=0.019 ± 0.005 (stat) ± 0.002 (syst)
- PDG 2007 values
- BR(J/e+e-)=5.94 ± 0.06%
- BR(’e+e-)=0.743 ± 0.018%
- BR(’J/+X)=56.9 ± 0.9%
-  (’)/(J/)=0.15 ± 0.04
- Feed-down fraction of J/ from ’ is **0.086 ****±**** 0.025**.

- J/

- ’

## b-quark cross section obtained by electron-hadron correlation (p+p 200GeV, Run-5&6)

- PHENIX preliminary
- dbb-bar/dy|y=0=1.34 ± 0.38(stat) +0.74-0.64(syst) b
-  bb-bar=4.61 ± 1.31(stat) +2.57-2.22(syst) b
- PDG 2007 values
- BR(bJ/+X)=1.16 ± 0.10%
- BR(bJ/+X)bb-bar=53 +34-30 nb
- Feed-down fraction of J/ from b and b-bar quarks is **0.036 ****+0.025****-0.023**.

- __

- Y. Morino’s talk (XIV-5, Friday, finished)

**8/22**

## Summary of feed-down measurements 

- Summary of feed-down measurements

- In p+p collisions at √s=200GeV, J/ is produced via
-  cJJ/+ decays : <42% (90% C.L.)
-  ’J/+X decays : 8.6 ± 2.5%
- b quarkJ/+X decays : 3.6 +2.5-2.3%
- Direct J/ production : the rest
- Our knowledge of J/ production became much better.
- R.Vogt’s fractions are almost consistent with these measured fractions.

**9/22**

## Motivation to measure J/ in Cu+Cu collisions at 200 GeV 

- More precise measurement in small Npart than in Au+Au collisions
- Systematic measurement across entire Npart range
- Cold nuclear matter effects might be dominant
- Where is the starting point of J/ suppression?
- Higher luminosity gives higher statistics

**10/22**

## Statistics of J/ in Cu+Cu 200 GeV running

- Statistics of J/ in Cu+Cu 200 GeV running

- Run-5 Cu+Cu 200GeV
- January 18, 2005-March 6, 2005
- Midrapidity (|y|<0.35)
- 2.1 nb-1 (6.1B events)
- 2000 J/
- Forward rapidity (1.2<|y|<2.2)
- 1.3 nb-1 (3.8B events)
- 9000 J/

- North arm
- 1.2<y<2.2

- South arm
- -2.2<y<-1.2

- MinBias
- 0-94%

- Central arm
- |y|<0.35

**11/22**

**12/22**

- Invariant cross sections of J/

- J/ was measured from pT=0GeV/c to beyond pT =5GeV/c.

## RAA vs pT  

**13/22**

- No strong pT dependence. RAA will be extended to >5GeV/c soon.

## <pT2> vs Npart 

**14/22**

- <pT2> vs Npart

- Recombination of charm quarks could cancel the Cronin and leakage effects.
- Need more statistics to draw a conclusion.
- L. Yan, P. Zhuang and N. Xu, Phys. Rev. Lett. 97, 232301 (2006)
- X. Zhao and R. Rapp, arXiv:0812.2407 [hep-ph]

- without recombination

- with recombination

## RAA vs rapidity 

- RAA vs rapidity

**15/22**

- No strong rapidity dependence.
- The RMS width of the rapidity distribution is identical within ~2-3%
- uncertainties in p+p and in all centrality classes for Cu+Cu collisions.

## RAA vs Npart

- RAA vs Npart

**16/22**

- Suppression by a factor of ~2 in central Cu+Cu collisions

## Rapidity dependent “effective” nuclear breakup cross sections from d+Au

**17/22**

- “Effective” breakup cross section is lager at forward rapidity than at midrapidity

- arXiv:0801.0220 [nucl-ex]
- arXiv:0711.3917 [nucl-ex]

- EKS shadowing model

- NDSG shadowing model

- Forward rapidity:
- d going direction

- Backward rapidity:
- Au going direction

- Midrapidity

- EKS: Eur. Phys. J. C 9. 61 (1999)
- NDSG: Phys. Rev. D 69, 074028 (2004)

## Rapidity independent 

- Rapidity independent
- breakup cross sections

- Rapidity dependent
- “effective”
- breakup cross sections

**18/22**

- CNM effects at forward rapidity are lager than at midrapidity

- arXiv:0711.3917 [nucl-ex]

- arXiv:0801.0220 [nucl-ex]

## Comparison with Au+Au results

**19/22**

- Phys. Rev. Lett. 98, 232301 (2007), arXiv:nucl-ex/0611020

- With rapidity dependent “effective” breakup cross sections

- Cu+Cu and Au+Au data agree well.
- J/ suppression below CNM effects seems to start at Npart~200/100 at mid/forward rapidity.
- Rapidity narrowing in central Au+Au collisions is consistent with CNM effects.

## J/ at forward rapidity in Au+Au 200GeV with Run-7 data 

- J/ at forward rapidity in Au+Au 200GeV with Run-7 data

**20/22**

- Statistics will increase
- by a factor of 3 from
- Run-4 data.
- Preliminary Run-7 result
- at forward rapidity is consistent with published Run-4 result.

## J/ in d+Au 200GeV with Run-8 data (2.7nb-1(Run-3)81nb-1)

**21/22**

- 30 times larger statistics will reduce uncertainties of CNM effects.

## Conclusion

- Feed-down fractions of J/ in p+p collisions have been measured.
- Precise Cu+Cu data has been obtained.
- Cu+Cu and Au+Au data has been compared to cold nuclear matter effects extrapolated from updated d+Au data.
- CNM predictions agree with data in the small Npart region.
- J/ suppression seems to start at Npart~200 at midrapidity and ~100 at forward rapidity.
- Although CNM uncertainties are still large, they will be reduced by Run-8 d+Au data.

**22/22**

## Backup slides

## Updated J/ in Run-3 d+Au