# Presentation: 680346

## Marzia  Rosati
mrosati@iastate.edu
Iowa  State  University

**Marzia  Rosati**
**mrosati@iastate.edu**
**Iowa  State  University**

- Quarkonium production from d-Au to Au-Au

**Hard Probes 2004**
**Ericeira, Portugal**
**November 5, 2004**

## Outline

**Charmonium at RHIC**
**The PHENIX Detector**
**Charmonium Measurements in PHENIX**
-  p-p Collisions
- d-Au Collisions
- First Measurement in Au-Au Collisions
**Summary, conclusions, and outlook.**

## Charmonium Physics at RHIC

**We expect a screening of the attractive potential as we approach the deconfinement transition**
**This color screening may results in a decrease in the number of heavy quarkonia states **
**Alternative models predict enhancement from     c-cbar  coalescence as the collision volume cools.**

- Comparisons between various collision species are very important.
- Studies done via both dielectron and dimuon channels in PHENIX.

## PHENIX Collaboration

**  ****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****	**

**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**

## PHENIX Detector

**PHENIX Detector**

## Electron Identification

**PHENIX has excellent electron identification capabilities.**
-  Ring Imaging Cherenkov Counter - threshold selection
-  TEC/TRD - dE/dx and TR measurement
-  Electromagnetic Calorimeter - Energy-Momentum match

- EMC energy / Momentum

- All charged tracks

- Background

- Net signal

- Real

- Apply RICH cut

## Di-electron analysis

**Identify electron**
- RICH ring cut
- 0.5 < E/p < 1.5
**Di-electron invariant mass spectra**
**Subtract combinatorial background**
**Signal = ****N****+-**** - ****( N****++**** + N****--****) ****Count J/******
**Correct for acceptance and efficiencies**
**      ******** ****Cross section**

**Example : dAu sample**

**Mass Resolution ~ 100 MeV**

## Muon Measurements

## Di-muon analysis

**Identify muons**
- Depth in Identifier
**Di-muon inv. mass spectra**
**Subtract combinatorial backgrounds **
- Signal = N+- -2(N++)(N--)
**Work in progress to quantify physical backgrounds :**
- Open charm & beauty,       Drell-Yan,   a hint of ’
**      ****For now: fit gauss J/********+exp bg**
**Correct for acceptance and efficiencies **
**       ******** ****Cross section**

- Example : dAu North Arm Sample

- Mass Resolution ~ 150 to 200 MeV

## Do we understand the basic production mechanism?

**The production mechanism of charmonium in p-p collisions is not yet well understood.**
- Color evaporation model, Color singlet model, Color octet model
- Polarization, Rapidity dependence (electron and muon channels)
- Production of J/, ',.. states
**We need a good measurement of J/******** cross section in p+p at RHIC**
- Base line for pA and AA

## Integrated cross-section : 
234 ± 36 (stat) ± 34 (sys) ± 24(abs) nb 

**Integrated cross-section : **
**234 ± 36 (stat) ± 34 (sys) ± 24(abs) ****n****b **

**e****+****e****–**

******+********–**

- Results consistent
- with shapes from
- various models and PDF.
- Take the PYTHIA
- shape to extract
- our cross-section

**Phys.Rev.Lett.92, 051802,2004 **

**J/********  in p+p Collisions @ 200 GeV (2002 data)**

## Energy Scaling

**Phenomenological fit for average pT**
- p = 0.531, q= 0.188
**Cross-section well described by e.g. Color Evaporation Model.**

## J/  in p+p Collisions @ 200 GeV (2003 Preliminary data)

- total cross section from Run3 data BR.tot = 159 nb  8.5 %  12.3 %

- total cross section from Run2 data BR.tot = 234  36  34  24 nb

**J/********  in p+p Collisions @ 200 GeV**** ****(2003 Preliminary data)**

## Charmonium in d-Au Collisions

**Study of "normal nuclear effects": shadowing and energy loss**
- Nuclear dependence of (J/): A or abs (nuclear absorption)
- dE/dx not expected to be significant effect at RHIC energies
- Overall absorption expected
- Base line for AA

## d-Au Collisions

**PHENIX measurements cover different ranges of the Au parton momentum fraction where shadowing and anti-shadowing are expected**
**South (y < -1.2) : large X****2**** (in gold)   ~ 0.09**
**Central (y ~ 0) : intermediate X****2        ****~ 0.02**
**North (y > 1.2) : small X****2**** (in gold)    ~ 0.003**

***Eskola, Kolhinen, Vogt hep-ph/0104124***

**PHENIX ****μ, ****North     ****PHENIX ********, SOUTH**
**                        ****PHENIX ****e**

- d

- Au

- North Muon Arm

- South Muon Arm

- Central Arm

## Cross section versus pT

- High x2 ~ 0.09

- Low x2
- ~ 0.003

- J**/******************

- Cross section versus pT

**p****T**** is broadened for dAu**

- <pT2> =
- <pT2>dAu – <pT2>pp
- 1.77 ± 0.35 GeV2
- 1.29 ± 0.35 GeV2
- (preliminary)

- J**/******************

## pT broadening comparable
to lower energy
(s = 39 GeV in E866)

**High x****2**
**~ 0.09**

**Low x****2**
**~ 0.003**

**p****T**** broadening comparable**
**to lower energy**
**(********s = 39 GeV in E866)**

**dAu/pp versus p****T**

## J/ Rapidity Distribution in dAu and pp 

## Data favors (weak) shadowing + (weak) absorption ( > 0.92)
With limited statistics difficult to disentangle nuclear effects.

**1****st**** J/****ψ****’s at large negative rapidity!**

**Low x****2**** ~ 0.003**
**(shadowing region)**

**Data favors (weak) shadowing ****+ (weak) absorption (******** > 0.92)**
**With limited statistics difficult to disentangle nuclear effects.**

- RdA

**dAu/pp versus rapidity**

## Charmonium in Au-Au Collisions

**Study of "medium effect" in high density matter**
- J/ suppression : signature of QGP
- J/ formation by c quark coalescence
**Experimental plan is to establish that the (to be observed) charmonium suppression/enhancement pattern results from QGP**
- Study vs. pT
- Study vs. centrality
- Study in lighter systems
- Study vs. a control

## Disfavor models with enhancement relative to binary collision scaling. Cannot discriminate between models that lead to suppression relative     to binary collision scaling.

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

**J/********  in Au+Au Collisions @ 200 GeV**** (2002 data)**

## J/  in Au+Au Collisions @ 200 GeV (2004 data)

- J/  signal

**J/********  in Au+Au Collisions @ 200 GeV**** (2004 data)**

**Analysis underway of a data sample ****(240 ********b****-1****minbias  events, 270 TB)**
** **
**     ****Example of Dimuon invariant mass - South arm - Peripheral AuAu Collisions**
**(40-92%)**
**     ****(~30% of data set)**
**Example of Dielectron invariant mass  minium bias sample**
**( < 10% of data set)**

**PHENIX Work in progress**

## Near future at RHIC

**Full exploration of J/ ********and********’ production versus “N****binary****”**
**Look forward to future runs with high luminosity where also studies for different collision species and with varying energy can be made**
**Cool-down of the RHIC ring for the upcoming run will start on Nov 8**
- CuCu collisions and long p-p run

## Summary

**p+p collisions: **
- we measured total and differential J/ cross section, vs pt and y
**d+Au collisions: **
-  evidence for weak shadowing and weak nuclear absorption
-  evidence for pt broadening when comparing
-                                                               <pt2>d+Au vs <pt2>p+p
**Au+Au collisions:**
- Run2 (2002) has low luminosity
-  Run4 (2004) has 50 times more data, presently being analyzed
- New Cu-Cu run about to start
-              **STAY TUNED !**
**More on “Heavy flavor production in PHENIX” by Olivier Drapier tomorrow**