Centrality Dependence of 0 Production in Au+Au

Collisions at = 62.4 GeV

Stefan Bathe (UCR)for the PHENIX collaboration

DNP Fall Meeting, October 2004

NNs

DNP04 Stefan Bathe, PHENIX 2

Hard Scattering and RAA• Hard processes

– yield scales with Ncoll

– reason: • small cross section• incoherent superposition

• Nuclear Modification Factor RAA

• In the absence of nuclear effects: RAA=1 at high pT

no effect

strongsuppression

TNNfAA

TAAAA

d/d

d/d0

0

pT

pNR

fAAfTN inel

NNcoll

DNP04 Stefan Bathe, PHENIX 3

• Strong suppression at 130 and 200 GeV

• No suppression at 17 GeV

0 RAA, Central Events,Different √s

62.4 GeV Au+Au

WA98, EPJ C 23, 225 (2002)

[ new reference compiled by: D.d'Enterria nucl-ex/0403055]

PHENIX, PRL 88, 022301 (2002)

• Energy loss predicted to be proportional to – system size – gluon density

• changing s – changing gluon density– changing expected energy

loss– test of jet-quenching

theory

• Why 62.4 GeV?– Between SPS and RHIC on

logarithmic scale of √s– Wealth of p+p reference

data

200 GeV: new preliminary result

to higher pT

DNP04 Stefan Bathe, PHENIX 4

62.4 GeV p+p 0 Reference

+/-25% uncertainty

• 0 data from ISR• Corrected for (when

necessary) – hadronic decay– direct photons

• Global fit:

• Fit and data cross-checked by NLO calculation

• ±25% systematic uncertainty

DNP04 Stefan Bathe, PHENIX 5

PHENIX Setup

• Central spectrometer arms || < 0.35– 0 via 0

• Lead scintillator calorimeter (PbSc)

• Lead glass calorimeter (PbGl)

DNP04 Stefan Bathe, PHENIX 6

0 Spectra at 62.4 GeV

0 data in min. bias, 0-10%, and 10-30%, and 30-60% most central collisions up to pT = 7GeV/c

• Small systematic uncertainty : 9~12%

DNP04 Stefan Bathe, PHENIX 7

RAA for 0 at 62.4 GeV

• Ratios close to unity at pT ~ 2.5 GeV/c, then decreasing

• Same tendency as 200 GeV Au+Au

• Less suppression at intermediate pT (compared to 200 GeV)

Ncoll for peripheral events not yet

understood

DNP04 Stefan Bathe, PHENIX 8

I. Vitev nucl-th/0404052

Adil & Gyulassy nucl-th/0405036

RAA

(π0) ~ 0.5 - 0.3

Predictions for RAA at 62.4 GeV

DNP04 Stefan Bathe, PHENIX 9

RAA for 0 at 62.4 GeV

Vitev nucl-th/0404052

• Reasonably good agreement (esp. high pT) within uncertainties

• Uncertainty in the pT shape (esp. low p

T) of p+p reference ...

DNP04 Stefan Bathe, PHENIX 10

RAA for 0 at 62.4 GeV

charged referencewith h/ ratio used here (cf. talk by J. Jia, CB 4)

Agreement with charged reference better:Better p+p reference needed

Vitev nucl-th/0404052

DNP04 Stefan Bathe, PHENIX 11

RAA for Charged Hadrons

0

charged

charged

00-10%

10-30%charged reference is used here

62.4 GeV

• 0 yield is multiplied by 1.6• Discrepancy between

charged and 0

• Neutral pions more suppressed than h+/- at intermediate pT

• Large proton contribution up to at least 4GeV/c (cf. talk by T. Chujo, CB 6)

DNP04 Stefan Bathe, PHENIX 12

0 RAA, Central Events,Different √s

WA98, EPJ C 23, 225 (2002)

[ new reference compiled by D.d'Enterria nucl-ex/0403055]

PHENIX, PRL 88 022301 (2002)

• Suppression at 17 GeV and 62.4 GeV similar at medium pT

• 62.4 GeV expected lower

• Better reference needed!

DNP04 Stefan Bathe, PHENIX 13

Summary• Suppression at 200 GeV established to higher pT

• 0 spectra at 62.4 GeV for three centrality classes

• RAA for 0-10% and 10-30% most central events

• Suppression at intermediate pT less than in 200 GeV, but similar to 17 GeV

• Suppression in agreement with energy-loss calculations

• 0 more suppressed than h+/- at intermediate pT

• Result strongly depends on reference• Better reference needed!

DNP04 Stefan Bathe, PHENIX 14

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 PauloChina Academia Sinica, Taipei, Taiwan China Institute of Atomic Energy, Beijing Peking University, BeijingFrance 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, NantesGermany University of Münster, MünsterHungary Central Research Institute for Physics (KFKI), Budapest Debrecen University, Debrecen Eötvös Loránd University (ELTE), Budapest India Banaras Hindu University, Banaras Bhabha Atomic Research Centre, BombayIsrael Weizmann Institute, RehovotJapan 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, SeoulRussia 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. PetersburgSweden Lund University, Lund

12 Countries; 58 Institutions; 480 Participants*

*as of January 2004

DNP04 Stefan Bathe, PHENIX 15

Backup Slides

DNP04 Stefan Bathe, PHENIX 16

p/pi ratio

DNP04 Stefan Bathe, PHENIX 17

h/pi ratio