1. Rapidity dependence of charged particle yields with BRAHMS for Au+Au at 200 GeV Djamel Ouerdane for the BRAHMS collaboration Quark Matter 2002 Nantes, July 17-24 BRAHMS

2. Djamel Ouerdane - BRAHMS Collaboration 2 The BRAHMS Collaboration I.G. Bearden 7, D. Beavis 1, C. Besliu 10, Y. Blyakhman 6, J.Brzychczyk 4, B. Budick 6, H. Bøggild 7, C. Chasman 1, C. H. Christensen 7, P. Christiansen 7, J.Cibor 4, R.Debbe 1, E. Enger 12, J. J. Gaardhøje 7, M. Germinario 7, K. Grotowski 4, K. Hagel 8, O. Hansen 7, A.K. Holme 12, H. Ito 11, E. Jacobsen 7, A. Jipa 10, J. I. Jordre 10, F. Jundt 2, C.E.Jørgensen 7, R. Karabowicz 4, T. Keutgen 9, E. J. Kim 5, T. Kozik 3, T.M.Larsen 12, J. H. Lee 1, Y. K.Lee 5, G. Løvhøjden 2, Z. Majka 3, A. Makeev 8, B. McBreen 1, M. Mikkelsen 12, M. Murray 8, J. Natowitz 8, B.S.Nielsen 7, K. Olchanski 1, D. Ouerdane 7, R.Planeta 4, F. Rami 2, D. Roehrich 9, B. H. Samset 12, D. Sandberg 7, S. J. Sanders 11, R.A.Sheetz 1, Z.Sosin 3, P. Staszel 7, T.S. Tveter 12, F.Videbæk 1, R. Wada 8, A.Wieloch 3 and I. S. Zgura 10 1 Brookhaven National Laboratory, USA, 2 IReS and Université Louis Pasteur, Strasbourg, France 3 Jagiellonian University, Cracow, Poland, 4 Institute of Nuclear Physics, Cracow, Poland 5 Johns Hopkins University, Baltimore, USA, 6 New York University, USA 7 Niels Bohr Institute, Blegdamsvej 17, University of Copenhagen, Denmark 8 Texas A&M University, College Station. USA, 9 University of Bergen, Norway 10 University of Bucharest, Romania, 11 University of Kansas, Lawrence,USA 12 University of Oslo Norway

3. BRAHMS Djamel Ouerdane - BRAHMS Collaboration 3 Outline of the talk The BRAHMS Experiment in a few words The BRAHMS acceptance Building particle spectra with BRAHMS Particle Spectra from y = 0 to … y = 3! Inverse slope parameter systematics : Flow vs y Strangeness : Kaon to Pion ratio vs y and Rapidity density dN/dy vs Rapidity Conclusion

4. BRAHMS Djamel Ouerdane - BRAHMS Collaboration 4 The BRAHMS Experiment 95° 30° 15° 2.3°

5. BRAHMS Djamel Ouerdane - BRAHMS Collaboration 5 The BRAHMS Experiment 95° 30° 15° 2.3° Momentum [GeV/c] Time of Flight at 4.5 m [ns] PID with the Mid-Rapidity Spectrometer

6. BRAHMS Djamel Ouerdane - BRAHMS Collaboration 6 The BRAHMS Experiment 95° 30° 15° 2.3° C1 π threshold TOF1 PID with the Front-Forward SPECTROMETER

7. BRAHMS Djamel Ouerdane - BRAHMS Collaboration 7 The BRAHMS Experiment 95° 30° 15° 2.3° PID in the Back-Forward Spectrometer RICH

8. BRAHMS Djamel Ouerdane - BRAHMS Collaboration 8 Acceptance covered Many field and angle settings = Many experiments!! (real data)

9. BRAHMS Djamel Ouerdane - BRAHMS Collaboration 9 Building spectra with BRAHMS

10. BRAHMS Djamel Ouerdane - BRAHMS Collaboration 10 Particle Spectra at mid-rapidity Centrality : 0 – 10% most central negative and positive : same trend Protons and pions converge around p T  2 GeV/c

11. BRAHMS Djamel Ouerdane - BRAHMS Collaboration 11 Particle Spectra at forward Rapidity (y = 3) Centrality : 0 – 10% most central p and  + converge at 1.2 GeV  - and anti-protons don’t p clearly over K + NOT over K -

12. BRAHMS Djamel Ouerdane - BRAHMS Collaboration 12 Effective temperature vs Mass Strong mass dependence Flow at all covered rapidities Slopes from exponential fit of p T spectra Negative  Positive

13. BRAHMS Djamel Ouerdane - BRAHMS Collaboration 13 Strangeness : ratio K/  Same evolution… Different value for K - /  - at y = 3

14. BRAHMS Djamel Ouerdane - BRAHMS Collaboration 14 y = 3 similar to SPS Strangeness : K/  systematics with

15. BRAHMS Djamel Ouerdane - BRAHMS Collaboration 15 Protons ? … Rapidity density vs Rapidity (0-10% central) Come to J.H. Lee’s talk on net protons

16. BRAHMS Djamel Ouerdane - BRAHMS Collaboration 16 Conclusion BRAHMS measured the rapidity dependence of particle yields (0-10% central) Mid-rapidity : spectra in p T similar between positive and negative hadrons, protons and pions converging around 2 GeV/c Forward rapidity : difference between negative and positive, protons above positive kaons, convergence with pions at 1.2 GeV/c, anti-protons under negative kaons. Inverse slope parameter mass dependent at all rapidities covered (flow at all rapidities, decreasing towards forward y) Positive and negative strangeness content at nearly equal amount at y = 0 (cf David Sanberg and Peter Christianen’s poster on Particle Ratios), K/   0.15. At y = 3, divergence : positive ratio at 0.18, negative at 0.1, suggesting a narrower K - dN/dy distribution. Y = 3 ratios similar to SPS Rapidity density of pions and kaons measured from y = 0 to 3, dNdy highest at y = 0 with little decrease up to y = 1. Faster decrease for higher y, K - faster than K +