T.C.Awes, ORNL

Centrality Dependence of 0 Production in d+Au Collisions

T.C. Awes, ORNLFor the PHENIX Experiment

Fall DNP Tucson, AZ, October 30, 2003

T.C.Awes, ORNL

Quenching of Hard Scattered Partons

• In the presence of a dense strongly interacting medium, hard scattered partons will suffer soft interactions losing energy before fragmenting into jet of hadrons (“Jet Quenching”)

• Quenching is observed, but could it be due to initial state effect? (“Gluon Saturation”)

Hadrons

Leading Particle

Leading Particle

Hadrons

q,gq,g

Hadrons

Leading Particle

Leading Particle

Hadrons

q,gq,g

• Reference case: d+Au No produced medium.

T.C.Awes, ORNL

RAuAu : High PT 0 Suppression to at least 10 GeV/c

PRL 91 (2003) 072301

Binary scaling

Participant scaling

Factor ~4-5

pp

AuAubinaryAuAuAA Yield

NYieldR

/ ⟩⟨=

Large suppression in central AuAu - close to participant scaling at high PT

Peripheral AuAu - consistent with Ncoll scaling (large systematic error)

T.C.Awes, ORNL

Cronin Effect:(RAA>1) Charged hadrons vs. 0

• Different behavior between 0 and charged at pT = 1.5 - 5.0 GeV/c!

• d+Au data suggests flavor dependent Cronin effect.

d+Au

Au+Au

PHENIXPRL 91 072303 (2003) nucl-ex/0306021

Particle ID is important!

d+Au: Cronin Effect (RdA>1): Initial Multiple Collisions broaden PT

spectrum

T.C.Awes, ORNL

PHENIX Electromagnetic Calorimeter

PbSc• Highly segmented lead scintillatorsampling Calorimeter• Module size: 5.5 cm x 5.5 cm x 37 cmPbGl•Highly segmented lead glassCherenkov Calorimeter• Module size: 4 cm x 4 cm x 40 cm

Two Technologies - very important for systematic error understanding!Differences:•Different response to hadrons•Different corrections to get linearenergy response•Different shower overlap corrections

T.C.Awes, ORNL

d+Au Collision Centrality Determination

•Extract Ncoll and Npart based on Glauber model.

South Blick von der Seite North

BB

MuTr

MuID MuID

ZDC NorthZDC South

MVD

Central Magnet

North Muon Magnet

South Muon MagnetPeripheral

Central

Sum BBC Charge -> Multiplicity

Au d

• 0-20 % : 15.0 ± 1.0

• 20-40 % : 10.4 ± 0.7

• 40-60 % : 6.9 ± 0.6

• 60-88 % : 3.2 ± 0.3

Centrality <Ncoll>

• Centrality selection : Beam-Beam Counter South (Au) (BBC, ||=3~4)

T.C.Awes, ORNL

Centrality Dependence of d+Au Spectra

• Combined PbSc and PbGlresults

•0 Yields measured to ~10 GeV/c

T.C.Awes, ORNL

RdAu PbGl and PbSc Comparison

T.C.Awes, ORNL

RdAu 0 Centrality Dependence

• Weak increase with centrality (Cronin effect)

• d+Au centrality dependence opposite to Au+Au

• Strongly suggests Au+Au suppression is due to effect of dense produced matter

T.C.Awes, ORNL

RdAu 0 Centrality Dependence vs. Theory

Rd

Au

Nucl-th/0308029, Accardi and GyulassySession CC.002 FridayAM.

T.C.Awes, ORNL

and Charged Comparison (Ratio to fit)

F.Matathias, CC-7, Friday AM

T.C.Awes, ORNL

Central to peripheral

T.C.Awes, ORNL

Summary and Conclusions

• A strong suppression of 0 production is observed in central Au+Au collisions at RHIC possibly due to parton energy loss in the medium (result is not conclusive in itself).

• The 0 production in d+Au collisions shows no strong suppression at high-PT but rather an enhancement which increases with centrality (Cronin effect).

• Strongly indicative that the suppression effect in central Au+Au is due to the created QCD medium.

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 Georgia State University, Atlanta, GA University of Illinois 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, Ecole Polytechnique, CNRS-IN2P3, Palaiseau SUBATECH, Ecole des Mines de Nantes, CNRS-IN2P3, Univ. 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 University of Tokyo, Bunkyo-ku, Tokyo 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; 57 Institutions; 460 Participants

T.C.Awes, ORNL

BACKUP SLIDES

T.C.Awes, ORNL

RAA vs. RdA for Identified 0

d+Au

Au+Au

The dAu results (initial state effects only) suggest that the created medium is responsible for high pT suppression in Au+Au.

Neutral pions are measured with 2 independent Calorimeters – PbSc and PbGl: Consistency check.

PHENIX, PRL91 (2003) 072303.

T.C.Awes, ORNL

Centrality Dependence of RAA

More central collisions D.Kharzeev, E.Levin, L.McLerranhep-ph/0210332

PRL 91 (2003) 072301

The suppression increases smoothly with centrality - approximate Npart scaling.

Centrality dependence similar topredictions of Color Glass Condensate(AKA Gluon Saturation)-Suggests Initial state effect!?!

-Need p+Au (d+Au)

T.C.Awes, ORNL

Centrality Dependence

• Opposite centrality evolution of Au+Au compared to d+Au control.• Initial state enhancement (“Cronin effect”) in d+Au is suppressed

by final state effect in Au+Au. • Notice difference between 0 and h++h- .

Au + Au d + Au Control

Preliminary DataFinal Data

T.C.Awes, ORNL

Data vs Theory : 0

PHENIX Preliminary

0 d+Au (minbias) 200 GeV

0 Au+Au (0-5%) 200 GeV

Au+Au: I. Vitev and M. Gyulassy, hep-ph/0208108, to appear in Nucl. Phys. A; M. Gyulassy, P. Levai and I. Vitev, Nucl. Phys. B 594, p. 371 (2001).

Shadowing

Anti-shadowing

d+Au: I. Vitev, nucl-th/0302002 and private communication.

Energy loss + Shadowing + Cronin explains both Au+Au and d+Au!

Can dAu and AuAu centrality dependence also be explained?