# Presentation: 510284

## J/ measurements at STAR

- Zebo Tang (for the STAR Collaboration)
- (University of Science and Technology of China)
- (*Brookhaven ** National Laboratory*)

- Outline:
** ****Motivation and introduction**
** **
** ****J/******** spectra in p+p and Cu+Cu**
** ****J/********-hadron correlation in p+p **
** ****Summary and outlook**

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## D. Kharzeev, Hard Probs ‘08

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## High pT J/ in heavy ion collisions

**High p****T**** J/******** in heavy ion collisions**

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

**J/******** suppression at low p****T**** maybe only from excited stats (********’, ********c****)  **
- F. Karsch, D. Kharzeev and H. Satz, PLB 637, 75 (2006)
**Hot wind dissociation ******** high p****T ****direct J/******** suppression**

- Hot wind dissociation

- H. Liu, K. Rajagopal and U.A. Wiedemann
- PRL 98, 182301(2007) and hep-ph/0607062
- M. Chernicoff, J. A. Garcia, A. Guijosa hep-th/0607089

- T. Gunji, QM08

- NA50, EPJ39,335
- NA60, QM05
- PHENIX, PRL98,232301

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## Charmonium production mechanism in p+p

- Color singlet model (CSM) 1)   pQCD
- Color octet model   (COM) 2)  NRQCD
- Color evaporation model (CEM) 3)
- ...
- Contribution might be from:
- Gluon fusion
- Heavy quark fragmentation 4)
- Gluon fragmentation 5)
- Decay feed-down
- ...
- How do we distinguish different production
- mechanism and different source contribution?

*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/0202227*
*5)  K. Hagiwara et al., hep-ph/0705.0803*

**What’s the production mechanism at RHIC energy?**

- CDF measurement: PRL79,572

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## The STAR Detector

**The STAR Detector**

**Magnet**
**Coils**
**Central **
**Trigger**
**Barrel **
**(CTB)**
**ZCal**
**Time **
**Projection **
**Chamber**
**(TPC)**
**Year 2000**

**Barrel EM Cal (BEMC)**
**Silicon Vertex Tracker (SVT)****Silicon Strip Detector (SSD)**
**FTPC****Endcap EM Cal****FPD**
**TOFp, TOFr**
**PMD**
**Year 2001+**

- _Large acceptance: 2____ coverage at mid-rapidity_

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

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## Low pT J/ in p+p and Cu+Cu at 200 GeV

**Low p****T**** J/******** in p+p ****and Cu+Cu ****at 200 GeV**

**J/******** trigger**

- 0 < pT < 5.5 GeV/c

- p+p 200 GeV

- J/e+e-

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## High pT J/ in p+p at 200 GeV

**High p****T**** J/******** in p+p at 200 GeV**

**J/******** p****T **

**J/******** p****T **

- EMC+TPC electrons:
***1, p**T**>2.5 GeV/c*
- TPC only electrons:
***1, p**T**>1.2 GeV/c*

- EMC+TPC electrons:
***1, p**T**>4.0 GeV/c*
- TPC only electrons:
***1, p**T**>1.2 GeV/c*

**No background at p****T****>5 GeV/c**

**Reach higher p****T**** (~14 GeV/c)**

**p+p 2005**

**p+p 2006**

**EMC (High Tower) trigger:**
- 5 < pT < 14 GeV/c
** **

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## J/ spectra in p+p and Cu+Cu at 200 GeV

-  **Significantly extend p****T**** 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)**

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## J/+ccbar production puzzle

*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*

- The higher order contribution is significant and can not be neglected.

**NRQCD**** predict ****~0.1**

*K. Liu and Z. He, PRD 68, 031501 (2003)*

*B.L. Loffe and D.E. Kharzeev*
*PRD 69, 014016 (2004)*

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## NLO correction on spectra

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

*PHENIX, PRL 92, 05180 (2004)*

*S.P. Baranov and *
*A. Szczurek*
*arXiv:0710.1792*

**CSM NLO correction is huge**

*PRL98, 252002(2007*)

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## Compare to pQCD and NRQCD

**I: direct production**
**II: include ********c**** and ********’ feed-down**

- Statistics allow to distinguish different calculations
- NRQCD leave little room from parton fragmentation and B feed-down
- NNLO* under-predict at the highest pT bin

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## xT scaling in p+p collisions

**n is related to the**
**number of point-like**
**constituents taking**
**an active role in the**
**interaction**
**n=8: diquark scattering**
**n=4: QED-like scattering**

**x****T**** scaling:**** **
****** ****and proton at p****T****>2 GeV/c:  n=6.5±0.8   *****PLB 637, 161(2006)***
**J/******** at p****T****>5 GeV/c: n=5.6±0.2 **
******J/******** production: closer to 2********2 scattering**
**3.    Soft processes affect low p****T**** J/******** production**

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## Nuclear modification factor RAA

-  Double the pT range to 10GeV/c
-  Consistent with no suppression at high pT:   **R****AA****(p****T****>5 GeV/c) =**** 0.9±0.2**
-  Indicates RAA increase from low pT to high pT

-  Contrast to AdS/CFT prediction
-  Formed out of medium?
- Affected by heavy quark/gluon energy loss
-  Decay from other particles?
-  Color singlet?

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## Compare to SPS

- Similar trend also observed at SPS, might from different physics origin

- NA60, QM08

- NA50, 158 AGeV

*PLB499,85 and NPA774,59 *

**R****CP**

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## Disentangle contributions via Correlations

** **J/-hadron correlation can also shed light on different source contribution to J/ production
-  Might be used to distinguish CSM and COM

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## J/-hadron correlation

**Heavy quark fragmentation**

**Near side correlation**

- Good S/B ratio makes this
- measurement possible

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## J/hadron correlation in p+p

*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?

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## Constrain bottom yields

-  pQCD predicts significant BJ/
-  correlations shows low B contribution
-  can used to further constrain B yields
-  constrain correlation from jet fragmentation

**STAR Preliminary**

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## Yields in near/away side

-  **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****                      B********J/******** not a dominant contributor to inclusive J/******** **
**                      ****constrain J/******** production mechanism**

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## Summary

- J/ in p+p and Cu+Cu collisions:
- pT spectra in p+p:
**extended to ~14 GeV/c**
**follows x****T**** scaling with n=5.6 at p****T****>5 GeV/c, deviates from scaling at low p****T**
- J/-hadron azimuthal correlation in p+p:
**no significant near side correlation****constrain the contribution from B********J/********+X**
**away-side spectra consistent with **
**       ****h-h correlation ******** gluon or light quark fragmentation**
** **
-  J/ RAA
**indication of R****AA**** increasing at high p****T**

- production mechanisms:
**described by CEM and CSM**
**soft processes affect low p****T**** production**
**constrain decay contribution**
**constrain J/******** production from jet contribution (heavy flavor and gluon)**
**constrain production mechanism: CSM or COM**
**medium properties**

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## high-pt J/ in run8 dAu

- dAu EMC data sampled luminosity: 31 nb-1

- p+p equivalent: 13 pb-1

**Reduced material budget **
**by a factor of ~10**

**STAR Preliminary**

- Efficiency under going

**STAR Preliminary**

**FMS Data: 2.5<********<4.0 in process**

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## Future dramatic improvement of J / at low pT

- EMC+TOF+HFT (large acceptance):
- J/ production
- Different states predicted to melt at different T in color medium
- Charmonia (J/), bottonia ()

- PHENIX Acceptance:                    ||<0.35,=2*/2
- STAR TOF-Upgrade Acceptance: ||<0.9,=2*
**J****/******** yields from 1 billion minbias Au+Au events: ****43.8x10****-9****/0.040x10****9*****292*0.5*1.8*0.5=**** ****144,000********0.3% v****2**** error**
******J/************pp****   N   N****bin****   ********    y   R****AA**

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## Detector upgrades: HFT and MTD

**Heavy Flavor Tracker:**

**Muon Telescope Detector:**

**********e****+****e****-**** rejection**
**Topologically reconstruct**
**J/******** from B decay**

**Rejection power: ~16**

**Muon **
**identification**

- simulation

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## Backup

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## The STAR Detector

**The STAR Detector**

- Run8: without any inner tracker

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## Jpsi-h correlation from PYTHIA

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## High pT J/ in heavy ion collisions (Cont.)

**2-component approach****: dissociation + recombination**
-   RAA  decreases slightly or flat with pT  X. Zhao and R. Rapp, hep-ph/07122407
-   RAA  increase slightly with pT including formation time and B decay X.   Zhao, WWND2008
**Color singlet model****:**
-    RAA  increase with pT (formed out of medium) *F**. Karsch and R. Petronzio,  PLB   193(1987), 105 **; **J.P. Blaizot and J.Y. Ollitrault, PLB 199(1987),499*

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009

## Datasets

**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-p****T**** 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**

- Zebo Tang (WWND2009, Big Sky)

- 02/06/2009