# Presentation: 392104

##                   J/ Measurements 

**        ****in pp, dAu, and AuAu Collisions **
**      ****by the PHENIX Experiment at RHIC**

***Alexandre Lebedev, Iowa State University ***
***       ******for the PHENIX Collaboration***

-  **physics motivation**
** ****setup and data analysis**
** ****proton-proton**
** ****deutron-gold**
** ****gold-gold**
** ****summary and outlook**

## Motivation

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                        2*

-  Charm produced early in the collision, but decays weakly
-         ********lifetime is longer than that of the created medium.
-  Charm produced mainly via gluon fusion
-         ****probes gluon structure function in medium
-  Binding energy comparable to QGP screening energy
-         ****suppression of charmonium production if QGP is formed.
-          ****recent predictions of charmonium  enhancement.

** ****Compare different colliding systems from pp to AA**
** ****Study rapidity dependence (especially in pA)**
** ****Both dielectron and dimuon channels in PHENIX**

## Motivation (continued)

-           **Baseline for pA and AA**
**p-A** : Study of "normal nuclear effects":
-           a) gluon PDF modification (shadowing or anti-shadowing)
-           b) initial state multiple scattering
-           c) nuclear absorption
-           d) Cronin effect, etc.
-           **Baseline for AA**
**A-A** : Study of "medium effect" in high density matter
-     J/**** suppression : signature of QGP?
-     J/**** enhancement: recombination by charm quark coalescence

**Motivation (continued)**

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                        3*

##       ||<0.35,  Pelectron>0.2 GeV/c,

- Two central arms measure dielectrons
-       ||<0.35,  Pelectron>0.2 GeV/c,
-                     
-                **RICH, EMCal**

- Two muon arms measure dimuons
- 1.2<||<2.4, Pmuon> 2 GeV/c
- 

**The PHENIX Detector**

**Muon tracker, **
**Muon identifier **

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                        4*

## Muon Arms:   J/

- Central Arms:   J/****ee

- Muon Arms:   J/********

- Signal  =  N+    (N++ + N)

- Signal  =  N+   2 sqrt(N++N)

**The Data (dAu example)**

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                        5*

## pp cross section

**pp cross section**

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                        6*

- J/**** cross section from run3 pp data:    BRtot = 159 nb  8.5 %  12.3 %

## pp energy scaling

- Energy dependence of cross section is sensitive to gluon distribution function.
- PHENIX results are consistent with typical PDF and confirm gluon fusion picture
- of J/**** production. Both COM and CEM predictions are consistent with the data.

*Phenomenological fit*
*p=0.531; q=0.188*

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                        7*

## dAu: ''normal'' nuclear effects

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                        8*

-   Nuclear absorption:    dAu/pp/(2*197) < 1
-   Initial state multiple scattering:    PT broadening in dAu vs pp
-   Gluon PDF modification  (shadowing and anti-shadowing)

*Escola, Kolhinen, Vogt,*
*Nucl. Phys. A696(2001), p729*

- PHENIX North Muon Arm

- PHENIX Central Arms

- PHENIX South Muon Arm

## dAu: shadowing and anti-shadowing in PHENIX

**dAu: shadowing and anti-shadowing in PHENIX**

- In PHENIX, three rapidity ranges
- translate into three different momentum
- fractions XAu of gluons in gold nucleus.
- South Muon Arm:  -2.4<y<-1.2
-      ********large XAu ~0.09, expect anti-shadowing
- Central Arm: y~0
-      **** intermediate XAu ~ 0.02
- North Muon Arm:  2.4>y>1.2;
-      ****   small XAu ~0.003, expect shadowing

- XF = Xd – XAu
- XF = 2PZsqrt(s)
- XAu = 0.5(XF+sqrt(XF2+4))
*where*   = m2/s

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                        9*

## dAu/pp vs rapidity

**dAu/pp vs rapidity**

*     **Large (~0.09) X**Au**          Small (~0.003) X**Au*
*     **(anti-shadowing)             (shadowing)*

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                        10*

- Nuclear absorption: overall scale
- Shadowing: rapidity dependence
- PHENIX results indicate weak
- nuclear absorption and weak
-           shadowing in dAu

## dAu/pp vs X

**dAu/pp vs X**

- Initial state gluon energy loss might be
- expected to scale with XF (since XF ~ Xd).

- Shadowing can not be the only
- explanation since suppression does not
- scale with XAu, but with XF instead

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                        11*

- Au

## dAu/pp vs PT

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                     12*

-                <pt2>dAu – <pt2>pp =
- South Arm (Au direction):  1.77 ± 0.35 GeV2
- North Arm  (d direction)  :  1.29 ± 0.35 GeV2

**dAu/pp vs P****T**

## dAu/pp vs PT

- Multiple scattering in the initial state.
- Similar to what was observed by
- E866/NuSea at lower energies,
- see e.g. M.Leitch et al,
- PRL **84**(2000)3256

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                     13*

**dAu/pp vs P****T**

## J/ polarization in dAu

*and J/******** momentum in the lab frame.*

- Results consistent with no
- polarization, large error bars
- due to low statistics.

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                      14*

**J/******** polarization in dAu**

- PT>1.5GeV/c

- PT<1.5GeV/c

- PHENIX Preliminary

**J/******** production models predict different polarization.**
-      CEM and CSM:  no polarization
-      COM:  transverse at high PT
-      Ioffe and Kharzeev, hep-ph/0306176:   transverse
-                    (~0.35-0.40)  at low PT if QGP is formed
-      Khoze, Martin, Ryskin, and Stirling, hep-ph/0410020:
-                    longitudinal polarization at high PT

## AuAu run2

**AuAu run2**

- R. L. Thews, M. Schroedter, J. Rafelski,
- Phys Rev C 63, 054905
- Plasma Coalescence Model

- Binary Scaling

- Stat.Model
- Andronic et al nucl-th/0303036

- Absorption (Nuclear + QGP) + final-state
- coalescence
- Absorption (Nuclear + QGP)
- L. Grandchamp, R. Rapp,
- Nucl Phys A709, 415; Phys Lett B 523, 60

- y = 1.0

- y = 4.0

**Phys.Rev.C69, 014901,2004**** **

- Not enough statistics to make
- definitive conclusions, but the data
- disfavor enhancement.

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                      15*

## Run4 AuAu  and  run5 CuCu

**Run4 AuAu  and  run5 CuCu**

- Data analysis still in progress. J/**** peaks already seen in both
- Central and Muon Arms with small fraction of total statistics. Run4 is expected
- to collect 50 times more statistics than Run2. Run5 CuCu in progress.

*Better mass resolution in run4 and run5 in Central Arms *
*due to stronger magnetic field. Better S/B ratio.*

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                      16*

**Run4 AuAu**

**Run5 CuCu**

## Summary and Outlook

**pp**:        PHENIX measured cross section of J/**** production vs PT and
-              rapidity. Energy dependence of the cross section consistent
-              with typical gluon PDFs and confirm gluon fusion picture of
-              J/**** production.
**dAu**:    Evidence for weak shadowing and weak nuclear absorption.
-              Evidence for PT broadening, similar to PT broadening at lower
-              energies.
**AuAu**: Run2 had low luminosity. Data disfavor enhancement, but low
-              statistics do not allow to make conclusions.
-              Run4 has 50 times more data, analysis in progress.
-              Run5 CuCu is now in progress, more data on A dependence.

*Alexandre Lebedev, ISU              21**st** Winter Workshop on Nuclear Dynamics 02/10/2005                      17*

**Exciting new results by QM2005!**

##  12 Countries;  58 Institutions;  480 Participants*

**USA   Abilene Christian University, Abilene, TX **
**             ****Brookhaven National Laboratory, Upton, NY **
**             ****University of California - Riverside, Riverside, CA**
**             ****University of Colorado, Boulder, CO**
**             ****Columbia University, Nevis Laboratories, Irvington, NY**
**             ****Florida State University, Tallahassee, FL**
**             ****Florida Technical University, Melbourne, FL**
**             ****Georgia State University, Atlanta, GA**
**             ****University of Illinois Urbana Champaign, Urbana-Champaign, IL**
**             ****Iowa State University and Ames Laboratory, Ames, IA**
**             ****Los Alamos National Laboratory, Los Alamos, NM**
**             ****Lawrence Livermore National Laboratory, Livermore, CA**
**             ****University of New Mexico, Albuquerque, NM **
**             ****New Mexico State University, Las Cruces, NM**
**             ****Dept. of Chemistry, Stony Brook Univ., Stony Brook, NY**
**             ****Dept. Phys. and Astronomy, Stony Brook Univ., Stony Brook, NY  **
**             ****Oak Ridge National Laboratory, Oak Ridge, TN**
**             ****University of Tennessee, Knoxville, TN  **
**             ****Vanderbilt University, Nashville, TN****	**

*** ******12 Countries;  58 Institutions;  480 Participants****
***                          ******* as of January 2004***

**Brazil        University of São Paulo, São Paulo**
**China        Academia Sinica, Taipei, Taiwan**
**                  ****China Institute of Atomic Energy, Beijing**
**                  ****Peking University, Beijing**
**France      LPC, University de Clermont-Ferrand, Clermont-Ferrand**
**                  ****Dapnia, CEA Saclay, Gif-sur-Yvette**
**                  ****IPN-Orsay, Universite Paris Sud, CNRS-IN2P3, Orsay          **
**                  ****LLR, Ecòle Polytechnique, CNRS-IN2P3, Palaiseau**
**                  ****SUBATECH, Ecòle des Mines at Nantes, Nantes**
**Germany  University of Münster, Münster**
**Hungary   Central Research Institute for Physics (KFKI), Budapest**
**                  ****Debrecen University, Debrecen**
**                  ****Eötvös Loránd University (ELTE), Budapest **
**India         Banaras Hindu University, Banaras**
**                  ****Bhabha Atomic Research Centre, Bombay**
**Israel        Weizmann Institute, Rehovot**
**Japan       Center for Nuclear Study, University of Tokyo, Tokyo**
**                  ****Hiroshima University, Higashi-Hiroshima **
**                  ****KEK, Institute for High Energy Physics, Tsukuba **
**                  ****Kyoto University, Kyoto**
**                  ****Nagasaki Institute of Applied Science, Nagasaki**
**                  ****RIKEN, Institute for Physical and Chemical Research, Wako**
**                                               ****RIKEN-BNL Research Center, Upton, NY              **
**	****     ****Rikkyo University, Tokyo, Japan             **
**                  ****Tokyo Institute of Technology, Tokyo**
**                  ****University of Tsukuba, Tsukuba **
**                  ****Waseda University, Tokyo                    **
**S. Korea   Cyclotron Application Laboratory, KAERI, Seoul**
**                  ****Kangnung National University, Kangnung**
**                  ****Korea University, Seoul **
**                  ****Myong Ji University, Yongin City **
**                  ****System Electronics Laboratory, Seoul Nat. University, Seoul**
**                  ****Yonsei University, Seoul**
**Russia      Institute of High Energy Physics, Protovino **
**                  ****Joint Institute for Nuclear Research, Dubna **
**                  ****Kurchatov Institute, Moscow**
**                  ****PNPI, St. Petersburg Nuclear Physics Institute, St. Petersburg**
**                  ****St. Petersburg State Technical University, St. Petersburg**
**Sweden    Lund University, Lund**