1 / 17

Zhongbao Yin for the BRAHMS Collaboration

Key Results from the BRAHMS Experiment. Zhongbao Yin for the BRAHMS Collaboration. The BRAHMS experiment Baryon stopping High p T hadron production Summary. Outline. The BRAHMS Experiment. B road RA nge H adron M agnetic S pectrometers. Stopping.

evelyn
Download Presentation

Zhongbao Yin for the BRAHMS Collaboration

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Key Results from the BRAHMS Experiment Zhongbao Yin for the BRAHMS Collaboration

  2. The BRAHMS experiment Baryon stopping High pT hadron production Summary Outline

  3. The BRAHMS Experiment Broad RAnge Hadron Magnetic Spectrometers

  4. Stopping • Energy released for particle production • Information on the initial condition for the evolution of relativistic heavy-ion collisions • Landau model: full stopping+isentropic expansion • Bjorken scenario: transparency => net baryon poor region at mid-rapidity • Information on the baryon transport mechanism

  5. Moving away from the central region, the influence of the participant baryons becomes more and more important Stopping: pbar/p Au+Au @ 200 GeV • At Mid-rapidity • p-/p+= 1.01 ±0.04 • K-/K+ = 0.95 ±0.05 • pbar/p = 0.75 ±0.04 • Pair production is predominant • The ratios, within errors, are constant in the interval y=0-1 =>Considerable transparency PRL 90, 102301(2003)

  6. Stopping: Net Protons Au+Au @ 200 GeV HIJING withoutBaryon Junction is the least un-favoured. PRL 93, 102301(2004)

  7. y = 2.06 0.16 y = 2.04 0.10 Rapidity and Energy Loss E=26+-5GeV/n E= 30+-2GeV/n Rapidity loss saturates while around 75% of initial energy is available for particle production.

  8. Landau or Bjorken ? Au+Au @ 200 GeV Simplified Landau model predicts: dN/dy (y) of Gaussian with width 2 =ln(s/2mp) (Caruthers & Duong-van, PRD8(1973)859) PRL 94, 162301(2005)

  9. Hard Scattering recombination Study modifications of high pT production in AA, dA with respect to pp via Ncoll scaling at different rapidities to disentangle different effects

  10. Nuclear Modification Factors: RAA BRAHMS PRL91(2003)072305 RdAu : enhancement Large high pt suppression aslo at forward rapidity. RAA = (yieldAA/<Ncoll>)/yieldpp Rcp = (yieldcentral/<Ncoll>cent)/(yieldperipheral/<Ncoll>peripheral)

  11. RdA in d+Au Collisions BRAHMS PRL 93, 242303 (2004) Enhancement at mid-rapidity, while high pt suppression at h = 3.2

  12. Rcp in d+Au collisions • At mid-rapidity, stronger enhancement for more central collision, but reversed centrality dependence at forward rapidity. • Consistent with CGC prediction: PLB599(2004)23

  13. But… Recombination also works Hwa,Yang & Fries: PRC(2005)024902 with only the recombinationof soft and shower partons no multiple scattering, or gluon saturation put in explicitly

  14. RAA for identified hadrons BRAHMS Preliminary • Strong suppression for pions but no suppression for (anti-)protons at both mid-rapidity and forward rapidity

  15. p/p ratios in Au+Au collisions • Ratios are large compared with 0.2 from fragmentation of energetic partons • Ratios are smaller at forward rapidity while pion suppression persists. • Qualitative agreement with parton recombination with collective flow effect BRAHMS Preliminary

  16. Summary • RHIC reaches a net-baryon poor region at mid-rapidity • In Au+Au collisions at 200 GeV: • High pt suppression of charged hadrons and pions at both mid- and forward rapidities • No high pt (anti-)proton suppression at both mid- and forward rapidities • In d+Au collisions at 200 GeV: • significant reduction of the nuclear modification factor at forward rapidity and this suppression increases with rapidity and centrality

  17. I. Arsene10, I. G. Bearden7, D. Beavis1, C. Besliu10, B. Budick6, H. Bøggild7, C. Chasman1, C. H. Christensen7, P. Christiansen7, J. Cibor4, R. Debbe1, E. Enger12, J. J. Gaardhøje7, M. Germinario7, K. Hagel8, O. Hansen7, H. Ito1, 11, A. Jipa10, F. Jundt2, J. I. Jørdre9, C. E. Jørgensen7, R. Karabowicz3,E. J. Kim5, T. Kozik3, T. M. Larsen12, J. H. Lee1, Y. K. Lee5, S. Lindal12, R. Lystad9, G. Løvhøiden2, Z. Majka3, A. Makeev8, B. McBreen1, M. Mikelsen12, M. Murray8, 11, J. Natowitz8, B. Neumann11, B. S. Nielsen7, J. S. Norris11, 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 1Brookhaven National Laboratory, USA 2IReS and Université Louis Pasteur, Strasbourg, France 3Jagiellonian University, Krakow, 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 12 University of Oslo, Norway The BRAHMS Collaboration

More Related