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BRAHMS@RHIC

BRAHMS@RHIC. Nuclear Modification factors in Cu-Cu and Au-Au collisions Truls Martin Larsen Niels Bohr Institute for the BRAHMS Collaboration. What is the system size and energy dependence of high p T suppression?. The BRAHMS experiment What we measure: R cp and R AA

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BRAHMS@RHIC

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  1. BRAHMS@RHIC Nuclear Modification factors in Cu-Cu and Au-Au collisions Truls Martin Larsen Niels Bohr Institute for the BRAHMS Collaboration

  2. What is the system size and energydependence of high pT suppression? • The BRAHMS experiment • What we measure: • Rcp and RAA • Experimental results: • Au-Au collisions at • Au-Au collisions at • Cu-Cu collisions at • Comparing Au and Cu • Summary

  3. BRAHMS detector

  4. BRAHMS pT and h coverage Pseudo rapidity coverage: MRS: -0.1 < h < 1.2 FFS: 2.0 < h < 3.7 [MRS: Mid Rapidity Spectrometer] [FS: Forward Spectrometer]

  5. Central to peripheral ratio and the nuclear modification factor • Central to peripheral ratio: [H. Weber, UrQMD] • Nuclear Modification factor:

  6. RAA in AuAu at Unidentified hadrons (published): Strong suppression at mid- and forward rapidity in central collisions. (Systematic error shown as blue squares) [Phys. Rev. Lett. 91, 072305 (2003)]

  7. RAA in AuAu at Suppression at all h! RAA at h= 3.2 is only negative hadrons Only statistical errors shown RAA Preliminary Preliminary [Poster (4) by Catalin Ristea (session 1)]

  8. RAA in AuAu at Unidentified hadrons: RAA shows no suppression at midrapidity in central collisions Cronin enhancement in peripheral Only statistical errors shown pp reference is based on ISR data Preliminary

  9. Rcp in CuCu at Unidentified hadrons at h = 0 h = 0.9 h = 2.5 h = 3.0 Only statistical errors shown Preliminary

  10. Rcp in CuCu at Negative and positive hadrons Only statistical errors shown Preliminary

  11. RAA in CuCu at Unidentified hadrons at h = 0 and 1 Cronin enhancement at all centralities Only statistical errors shown Preliminary

  12. AuAu and CuCu at Preliminary

  13. System comparison RAuCu AuAu collisions shows suppression relative to CuCu collisions Only statistical error shown Preliminary

  14. Summary Semi peripheral collisions: AuAu @ 200 GeV: No suppression No rapidity dependence AuAu @ 62.4 GeV: Cronin Enhancement CuCu @ 62.4 GeV: Cronin enhancement • Central collisions: • AuAu @ 200 GeV: • Suppression • No rapidity dependence • AuAu @ 62.4 GeV: • No suppression • h= 0 ~ 1 • CuCu @ 62.4 GeV: • Cronin Enhancement RAuAu similar to RCuCu with the same <Nbin>

  15. BRAHMS Collaboration I.Arsene12, I.G. Bearden7, D. Beavis1, S.Bekele11, C. Besliu10, B. Budick6, H. Bøggild7 , C. Chasman1, C. H. Christensen7, P. Christiansen7, R.Clarke10, R.Debbe1, J. J. Gaardhøje7, K. Hagel8, H. Ito1, A. Jipa10, J. I. Jordre10, F. Jundt2, E.B.Johnson11, J.I.Jordre9, C.Jørgensen7, R. Karabowicz3, E. J. Kim11, T.M.Larsen7, J. H. Lee1, Y. K.Lee5, S.Lindal12, G. Løvhøjden2, Z. Majka3 , M. Murray11, J. Natowitz8, B.S.Nielsen7, D.Ouerdane7, R.Planeta3, F. Rami2, C.Ristea7, O.Ristea10, D. Röhrich9, B. H. Samset12, S. J. Sanders11, R.A.Sheetz1, P. Staszel3, T.S. Tveter12, F.Videbæk1, R. Wada8, H.Yang9, Z. Yin9,and I. S. Zgura10 1Brookhaven National Laboratory, USA, 2IReS and Université Louis Pasteur, Strasbourg, France 3Jagiellonian University, Kracow, 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 12 University of Oslo Norway 48 physicists from 12 institutions

  16. Nbin collisions CuCu at 62.4 GeV: <Nbin> (0-10%) = 142 ± 5.1 <Nbin> (10-20%) = 98.5± 9.5 <Nbin> (20-40%) = 51.6 ± 4.7 <Nbin> (40-60%) = 18.6 ± 1.9 • AuAu at 200GeV: • <Nbin> (0-10%) = 887 ± 39 • <Nbin> (10-20%) = 534 ± 46 • <Nbin> (20-40%) = 244 ± 23 • <Nbin>(40-60%) = 71.2 ± 7.3 • AuAu at 62.4 GeV: • <Nbin> (0-10%) = 754 ± 40 • <Nbin> (10-20%) = 459 ± 55 • <Nbin> (20-40%) = 217 ± 26 • <Nbin> (40-60%) = 70.0± 8.9

  17. Cu Cu positive hadrons

  18. Cu Cu negative hadrons

  19. pp reference yields • p-p yields only available at midrapidity: • eta=0 and eta=1 Fit to ISR data

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