1 Results from the BRAHMS experiment at RHIC Dieter Röhrich Fysisk institutt, Universitetet i Bergen for the BRAHMS collaboration • Experimental setup • Stopping • Particle production – Charged particle pseudo-rapidity distribution – Rapidity dependence of ratios of identified particles
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1 Results from the BRAHMS experiment at RHIC Dieter Röhrich Fysisk institutt, Universitetet i Bergen for the BRAHMS collaboration Experimental setup Stopping.
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1
Results from the BRAHMS experiment at RHIC
Dieter Röhrich Fysisk institutt, Universitetet i Bergen
for the
BRAHMS collaboration
• Experimental setup• Stopping• Particle production
– Charged particle pseudo-rapidity distribution– Rapidity dependence of ratios of identified particles
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BRAHMS collaboration
I.G. Bearden7, D. Beavis1, C. Besliu10, Y. Blyakhman6, J. Bondorf7, J.Brzychczyk4, B. Budick6, H. Bøggild7, C. Chasman1, C. H. Christensen7, P. Christiansen7, J.Cibor4, R.Debbe1,
J. J. Gaardhøje7, K. Grotowski4, K. Hagel8, O. Hansen7, H. Heiselberg7, A. Holm7, A.K. Holme12, H. Ito11, E. Jacobsen7, A. Jipa10, J. I. Jordre10, F. Jundt2, C. E. Jørgensen7, T.
Keutgen9, E. J. Kim5, T. Kozik3, T.M.Larsen12, J. H. Lee1, Y. K.Lee5, G. Løvhøjden2, Z. Majka3, A. Makeev8, B. McBreen1, M. Murray8, J. Natowitz8, B.S.Nielsen7, K. Olchanski1, D. Ouerdane7, R.Planeta4, F. Rami2, D. Roehrich9, B. H. Samset12, S. J. Sanders11, I. S.
Sgura10, R.A.Sheetz1, Z.Sosin3, P. Staszel7, T.S. Tveter12, F.Videbæk1, R. Wada8 and A.Wieloch3.
1Brookhaven National Laboratory, USA 2IReS and Université Louis Pasteur, Strasbourg, France
3Jagiellonian University, Cracow, Poland 4Institute of Nuclear Physics, Cracow, Poland
5Johns Hopkins University, Baltimore, USA
6New York University, USA 7Niels Bohr Institute, University of Copenhagen, Denmark
8Texas A&M University, College Station, USA 9University of Bergen, Norway 10University of Bucharest, Romania
11University of Kansas, Lawrence, USA 12University of Oslo, Norway
• Mean # of tracks/event ~1.4• TOF resolution roughly 25%
better than in 2000
• TOF K/p in FFS up to 5GeV/c
• TOF pi/K in FFS to 3GeV/c
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Hadron identificationFS (200AGeV) (3)
• Full PID in FS• Ring Imaging Cerenkov
Detector (RICH)
• Secondary ToF counter (H2)
PID up to 25 GeV/c
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Proton rapidity distribution
• AGS energies – Central collisions
– Energy dependence
B. Back et al., E917 Collaboration, Phys. Rev. Lett. 86 (2001) 1970
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Stopping
• Rapidity loss– energy
dependence
F. Videbæk, nucl-ex/0106017
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Net proton rapidity distribution
• SPS • central (6%) Pb+Pb, 158 GeV/nucl. • NA49
• RHIC• central (6%) Au+Au, sNN= 130 GeV
• BRAHMS, STAR
G. Cooper et al. (NA49 Collaboration), Nucl. Phys. A661 (1999) 362c-365c
C. Adler et al. (STAR), subm. Phys. Rev. Lett.; F. Videbæk (BRAHMS), QM01
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Net proton rapidity distribution – model predictions
• FRITIOF 7.02 • HIJING
• BRAHMS (central) preliminary
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Antiproton/proton ratio – rapidity dependence
• SPS • central (14%) Pb+Pb, 158 GeV/nucl. • NA49
• RHIC• central (40%) Au+Au, sNN= 130 GeV
• BRAHMS
G. Cooper et al. (NA49), Nucl. Phys. A661 (1999) 362c;G. Veres et al. (NA49), Nucl. Phys. A661 (1999) 383c
I.G. Bearden et al., (BRAHMS), Phys. Rev. Lett. 87 (2001)
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Antiproton/proton ratio – centrality dependence
• SPS • Pb+Pb, 158 GeV/nucl. • NA49
• RHIC• Au+Au, sNN= 130 GeV
• BRAHMS
G. Cooper et al. (NA49), Nucl. Phys. A661 (1999) 362c;G. Veres et al. (NA49), Nucl. Phys. A661 (1999) 383c I.G. Bearden et al., (BRAHMS), Phys. Rev. Lett. 87 (2001)
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Antiproton/proton ratio – energy dependence
• Energy systematics • RHIC, Au+Au sNN= 130 GeV
sNN= 200 GeV
RHIC, central Au+Au, BRAHMS
J.J. Gaardhøje, (BRAHMS), CIPPQG (2001)
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Particle production dNch/d @ snn= 130 GeV
• Charged particle pseudorapidity distribution
– SiMA, TMA, BB, TPC– Consistency between 4
independent detector systems
• Central 0-5% N(ch)d =
4050 ± 300
– dN(ch)/d (=0) = 553
1 36– FWHM of distribution
= 7.6 0.7
0-5%
10-20%
20-30%
30-40%
40-50%
5-10%
600
BRAHMS subm. Phys. Lett. B (2001)
65 AGeV + 65 AGeV
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Number of Participants
From HIJING
• dN/d ~ 3.2 per participant nucl. pair at =0 for central (0-5%); <Npart>=346
• Enhancement of particle production for central collisions at mid-rapidity
• At high rapidities ( >3) particle production scales with Npart