20-26 Feb. 2005 Lake Louise Eun-Joo Kim Parton energy loss, saturation, and recombination at BRAHMS...
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Transcript of 20-26 Feb. 2005 Lake Louise Eun-Joo Kim Parton energy loss, saturation, and recombination at BRAHMS...
20-26 Feb. 2005 Lake LouiseEun-Joo Kim
Parton energy loss, saturation, Parton energy loss, saturation, and recombination at BRAHMSand recombination at BRAHMS
Eun-Joo KimEun-Joo KimUniversity of KansasUniversity of KansasFor the BRAHMS For the BRAHMS collaborationcollaboration
20-26 Feb. 2005 Lake LouiseEun-Joo Kim
Hard scattering at RHIC Hard scattering at RHIC
study modifications modifications of high pT production in AA, dA with respect to pp via Ncoll scaling to learn about QCD dynamics : QQuark GGluon PPlasma and/or CColor GGlass C Condensate
RAA = (yieldAA/<Ncoll>)/yieldpp
Rcp = (yieldcentral/<Ncoll>cent)/(yieldperipheral/<Ncoll>peripheral)
coalescence
recombination
20-26 Feb. 2005 Lake LouiseEun-Joo Kim
Parton dynamics in a dense system of gluons differs from pQCD parton saturation
CColor GGlass CCondensate (effective field theory of dense gluon systems) controls gluon density in hadron hadron collisions initial conditions for the QGPQGP ?
Evolution & Saturation Evolution & Saturation
20-26 Feb. 2005 Lake LouiseEun-Joo Kim
BBroad RARAnge HHadron MMagnetic SSpectrometers
20-26 Feb. 2005 Lake LouiseEun-Joo Kim
Experimental observationsExperimental observations
RdAu : enhancement
Au+Au
RAuAu & Rcp ~ suppression strong effect of dense medium dependence ? baryon-meson ~ different behavior BRAHMS
preliminary
BRAHMS PRL91(2003)072305
Au+Au
Rapidity dependence
Particle dependence
20-26 Feb. 2005 Lake LouiseEun-Joo Kim
Rapidity dependant RRapidity dependant RdAudAu, R, Rcpcp
BRAHMS PRL93(2004)242303
Cronin like enhancement
increasing suppression
centrality dependence reversed at forward rapidities
consistent with CGC prediction: PLB599(2004) 23
20-26 Feb. 2005 Lake LouiseEun-Joo Kim
But… Recombination also But… Recombination also works!works!
with only the recombination of soft and shower partonsno multiple scattering, or gluon saturation put in explicitly
Hwa & Yang : nucl-th/04010111
BRAHMS dAu data PRL93(2004) 242303
=2.2 =3.2
d+Au
20-26 Feb. 2005 Lake LouiseEun-Joo Kim
RRAAAA for identified for identified hadronshadrons
=2.2
BRAHMS preliminary
- : strong suppression at ~0 & 2.2 in AuAu p : enhanced at ~2.2(AuAu), 3.2(dAu) collisions
Au+Au d+Au
20-26 Feb. 2005 Lake LouiseEun-Joo Kim
peripheral collision pp collision
RRcp cp for identified hadrons in for identified hadrons in AuAuAuAu
BRAHMS preliminary
RRcpcp for for --, K, K--, p at y~3.2 at p, p at y~3.2 at pT T ~ 2GeV/c~ 2GeV/c
Mass (or Baryon-Meson) dependent Rcp
Stronger centrality dependence for “Still” significant quark recombination at
y~3.2 ?
Y~3.2
20-26 Feb. 2005 Lake LouiseEun-Joo Kim
40-60%20-40%10-20%0-10% Energy dependence (SPSRHIC) pT = 3-4 GeV/c
pT=3-4GeV/c
RRAuAu AuAu at at ssNNNN = 62.4GeV = 62.4GeV
BRAHMS preliminary
~0.95
Suppression?
20-26 Feb. 2005 Lake LouiseEun-Joo Kim
p/p/ Ratios in AuAu Ratios in AuAu
BRAHMS : PreliminaryPHENIX : PRC69(2004) 034909Hwa & Yang : PRC70(2004) 024905Greco & Ko, PRC68(2003) 034904
p/- ratios lower at forward rapidity while suppression persists? no significant difference between y=0 and y~1 flow/mass effect ?
Hwa & Yang : y=0 Greco & Ko : y=0
20-26 Feb. 2005 Lake LouiseEun-Joo Kim
Ratios at Ratios at ~3.2 in dAu, ~3.2 in dAu, pppp
roughly as many protons as pions at high pT at forward rapidity in dAu
indicate other processes besides parton fragmentation
significant difference
small excess
20-26 Feb. 2005 Lake LouiseEun-Joo Kim
summarysummary BRAHMS has measured rapidity dependent nuclear modification factors and particle ratios in AuAu, dAu, and pp collisions. In AuAu collisions at sNN=200GeV, - High pT suppression (mesons) observed at y ~ 0, 2.2, and 3.2. - No strong rapidity dependent suppression. - Suppression is smooth with energy at 63, 130, and 200GeV. In dAu collisions at sNN=200GeV, - significant reduction of the nuclear modification factor at
forward rapidity and this suppression increases with and the
centrality. Initial state can be described by parton saturation (CGC). Baryon vs. Meson : Production and Nuclear Modification - Recombination/Coalescence can give reasonable explanation at intermediate pT in AuAu and dAu collisions.
20-26 Feb. 2005 Lake LouiseEun-Joo Kim
I.Arsene10, I. G. Bearden7, D. Beavis1, C. Besliu10, B. Budick6, H. Bøggild7, C. Chasman1,
C.H.Christensen7,P. Christiansen7, J. Cibor3, R. Debbe1, E. Enger12, J. J. Gaardhøje7, M. Germinario7, K. Hagel8, H. Ito1, A.Jipa10, F. Jundt2, J. I. Jørdre9, C. E. Jørgensen7,
R. Karabowicz4, E. J. Kim1,11, T. Kozik4 ,T. M. Larsen12, J. H. Lee1, Y. K. Lee5, S. Lindal12,
R. Lystad9, G. Løvhøiden12, Z. Majka4, A. Makeev8, M. Mikelsen12, M. Murray8, 11, J. Natowitz8,
B. Neumann11, B. S. Nielsen7, D. Ouerdane7, R. Planeta4, F. Rami2, C. Ristea10, O. Ristea10,
D. Röhrich9, B. H. Samset12, D. Sandberg7, S. J. Sanders11, R. A. Scheetz1, P. Staszel7,
T. S. Tveter12, F. Videbæk1, R. Wada8, Z. Yin9, I. S. Zgura10
1 Brookhaven National Laboratory, Upton, New York, USA2 IReS and Université Louis Pasteur, Strasbourg, France
3 Institute of Nuclear Physics, Krakow, Poland4 Smoluchkowski Inst. Of Physics, Jagiellonian University, Krakow, Poland
5 Johns Hopkins University, Baltimore, USA6 New York University, New York, USA
7 Niels Bohr Institute, University of Copenhagen, Denmark8 Texas A&M University, College Station, Texas, USA
9 University of Bergen, Bergen, Norway 10 University of Bucharest, Romania
11 University of Kansas, Lawrence, Kansas, USA 12 University of Oslo, Oslo, Norway
The BRAHMS CollaborationThe BRAHMS Collaboration