Eun-Joo Kim University of Kansas For the BRAHMS collaboration
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Transcript of Eun-Joo Kim University of Kansas For the BRAHMS collaboration
August 4-9, Quark Matter 2005
System and Rapidity System and Rapidity Dependence of Dependence of Baryon/Meson Ratios at Baryon/Meson Ratios at RHICRHIC
Eun-Joo KimEun-Joo KimUniversity of KansasUniversity of KansasFor the BRAHMS collaborationFor the BRAHMS collaboration
August 4-9, Quark Matter 2005
OutlineOutline
• The BRAHMS experiment• p/ ratios for different centrality
bins• p/ ratios for different systems• p/ ratios at different rapidities• Summary
August 4-9, Quark Matter 2005
BBroad RARAnge HHadron MMagnetic SSpectrometers
• AuAu, CuCu, pp sNN= 200 GeV• MRS at 90o (y=0) and full FS data at 4o (~3.2)• PID by TFW2, C4,TFW2, C4, RICHRICH
August 4-9, Quark Matter 2005
Particle IdentificationParticle Identification
C4C4
• TFW2 : /K ~ 2.5 GeV/c, K/p ~ 4.0 GeV/c with 2 cut• C4 : /K ~ 9 GeV/c• RICH : /K ~ 25 GeV/c, p ~ 35 GeV/c
MRS MRS TFW2TFW2 FS RICHFS RICH
August 4-9, Quark Matter 2005
Centrality dependent pbar/Centrality dependent pbar/- -
ratios ratios
Increase from peripheral to central in AuAu at sNN = 200 GeV
Ratio for peripheral AuAu
approaches to pp Ratios at forward
rapidity turn over at lower pT
than midrapidity
pp at y~0 : PHENIX preliminary pp at y~0 : PHENIX preliminary
BRAHMS PreliminaryBRAHMS Preliminary
• No Anti-Lambda No Anti-Lambda Feed-Down Correction!Feed-Down Correction!• Errors are statistical Errors are statistical only…only…
August 4-9, Quark Matter 2005
p/p/increases with system increases with system sizesize
++
--
August 4-9, Quark Matter 2005
Comparison of AuAu & CuCuComparison of AuAu & CuCu
pbar/- ratios are similar for different collision systems, and for a comparable number of binary collisions at y~0
and ~3.2
August 4-9, Quark Matter 2005
p/p/ ratios in CuCu collisions ratios in CuCu collisions
Centrality dependence for p/+ ratios is stronger
at ~3.2 than y~0, but pbar/- shows only slight centrality dependence at both
rapidities.
++ ++
-- --
August 4-9, Quark Matter 2005
pp
p/p/+ ratios vs. <Npart> in + ratios vs. <Npart> in CuCuCuCu
p/+ ratio integrated over 1.5<pT<2.5 GeV/c
at forward rapidity increase with centrality; smaller dependence seen at midrapidity
August 4-9, Quark Matter 2005
Rapidity and <NRapidity and <Npartpart> > dependencedependence
Y=0
~3.2
Strongrapidity dependence
pp
pp
August 4-9, Quark Matter 2005
Recombination & Recombination & CoalescenceCoalescence
Recombination and parton coalescence model describe
ratios at midrapidty and suggest radial flow
August 4-9, Quark Matter 2005
<pT> decrease with y : p ~ 10%,~ flat from y=0 to y~3
AMPT and 3D-Hydro model under-predict <pT> 3D-Hydro describe y-dependence qualitatively with a single Tth value (Tth = 100 MeV, Tch = 170 MeV)
Point : BRAHMS AuAu Curve : 3D Hydro (Hirano)Histo : AMPT
AuAu sNN= 200 GeV y~0
PRC72,014908(2005)
<p<pTT> vs. rapidity and > vs. rapidity and centralitycentrality
August 4-9, Quark Matter 2005
3D-Hydro Model for AuAu3D-Hydro Model for AuAu
- p/+ enhanced at forward rapidity, mainly from projectile?- Still high - Cronin, recombination, or flow?- The hydro calculation shown does not consider baryon nor
isospin chemical potentials: There is no rapidity dependence.- Particle ratio is fixed at chemical freezeout temperature
PHENIX : PRC69,034909(2004)PHENIX : PRC69,034909(2004)
BRAHMS PreliminaryBRAHMS Preliminary
August 4-9, Quark Matter 2005
SummarySummary
BRAHMS has studied the pT/centrality/rapidity/system dependence of the p/ratios for AuAu, CuCu and
pp - p/ ratios are enhanced in AA collisions compared to
pp - No other system dependence is observed - p/+ and pbar/- ratios show similar interplay between soft and hard processes for different
systems - However, there is strong rapidity dependence (baryo-chemical potential?) (p/ ratio)/<Npart> at constant independent of
system
August 4-9, Quark Matter 2005
The BRAHMS CollaborationThe BRAHMS CollaborationI.Arsene9,11, I.G. Bearden6, D. Beavis1, S.Bekele10, C. Besliu9, B. Budick5, H. Bøggild6 ,
C. Chasman1, C. H. Christensen6, P. Christiansen6, R.Clarke9, R.Debbe1,
J. J. Gaardhøje6, K. Hagel7, H. Ito1, A. Jipa9, J. I. Jordre8, F. Jundt2, E.B.Johnson10,
J.I.Jordre8, C.Jørgensen6, R. Karabowicz3, E. J. Kim10, T.M.Larsen6, J. H. Lee1,
Y. K.Lee4, S.Lindal11, G. Løvhøjden2, Z. Majka3 , M. Murray10, J. Natowitz7,
B.S.Nielsen6, D.Ouerdane6, R.Planeta3, F. Rami2, C.Ristea6, O.Ristea9,
D. Röhrich8, B. H. Samset11, S. J. Sanders10, R.A.Sheetz1, P. Staszel3, T.S. Tveter11,
F.Videbæk1, R. Wada7, H.Yang8, Z. Yin8, and I. S. Zgura9
1Brookhaven National Laboratory, USA2IReS and Université Louis Pasteur, Strasbourg, France
3Jagiellonian University, Krakow, Poland4Johns Hopkins University, Baltimore, USA
5New York University, USA6Niels Bohr Institute, University of Copenhagen, Denmark
7Texas A&M University, College Station. USA,8University of Bergen, Norway
9University of Bucharest, Romania10University of Kansas, Lawrence,USA
11University of Oslo, Norway
48 physicists from 11 institutions
August 4-9, Quark Matter 2005
Corrections in AuAuCorrections in AuAu
August 4-9, Quark Matter 2005
Net-p distributions? Net-p distributions?
Dynamics for Baryon/Meson is similar to p/+ and pbar/-?
August 4-9, Quark Matter 2005
p/p/ratios on Nratios on Ncollcoll
August 4-9, Quark Matter 2005
August 4-9, Quark Matter 2005