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Towards Matter-Antimatter Balance at RHIC

Towards Matter-Antimatter Balance at RHIC. BRAHMS. Antiparticle-to-particle ratios measured by BRAHMS. Djamel Ouerdane Niels Bohr Institute. XL International Winter Meeting on Nuclear Physics Bormio, January 21-26, 2002. The BRAHMS Collaboration.

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Towards Matter-Antimatter Balance at RHIC

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  1. Towards Matter-Antimatter Balance at RHIC BRAHMS Antiparticle-to-particle ratios measured by BRAHMS Djamel Ouerdane Niels Bohr Institute XL International Winter Meeting on Nuclear Physics Bormio, January 21-26, 2002

  2. The BRAHMS Collaboration I.G. Bearden7, D. Beavis1, C. Besliu10, Y. Blyakhman6, J.Brzychczyk4, B. Budick6, H. Bøggild7, C. Chasman1, C. H. Christensen7, P. Christiansen7, J.Cibor4, R.Debbe1, E. Enger12, J. J. Gaardhøje7, M. Germinario7, K. Grotowski4 , K. Hagel8, O. Hansen7, A.K. Holme12, H. Ito11, E. Jacobsen7, A. Jipa10, J. I. Jordre10, F. Jundt2,C.E.Jørgensen7, R. Karabowicz4 , 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. Mikkelsen12, M. Murray8, J. Natowitz8, B.S.Nielsen7, K. Olchanski1, D. Ouerdane7, R.Planeta4, F. Rami2, D. Roehrich9, B. H. Samset12, D. Sandberg7, S. J. Sanders11, I. S. Sgura10, R.A.Sheetz1, Z.Sosin3, P. Staszel7, T.S. Tveter12, F.Videbæk1, R. Wada8, A.Wieloch3 and I. S. Zgura10 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, Blegdamsvej 17, 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 Djamel Ouerdane - Niels Bohr Institute

  3. BRAHMS : what, where, when ? Data reconstruction : Collision vertex and centrality Particle identification Antiparticle to particle ratios (Au+Au at 200 GeV) Centrality and Transverse Momentum dependence Ratios as a function of rapidity Summary and things to come Outline of the talk Djamel Ouerdane - Niels Bohr Institute

  4. BRAHMS at The Relativistic Heavy Ion Collider BRAHMS Year 2001 achievements Au+Au at GeV BRAHMS Physics running from July 7 to November 26 More than 15 G events recorded with BRAHMS Djamel Ouerdane - Niels Bohr Institute

  5. BRAHMS Acceptance Particle IDentification • PID in MRS via TOFW • PID in FS via • TOF1, C1, TOF2 and RICH Transverse momentum [GeV/c] Rapidity Djamel Ouerdane - Niels Bohr Institute

  6. z ? BBR BBL • Δt in BBC measurements : 0.65 cm • Combining hits in TPM1: 0.2 cm Determination of Collision Vertex Djamel Ouerdane - Niels Bohr Institute

  7. Multiplicity Centrality Silicon Strips Plastic Scintillator Tiles Determination of Collision Centrality Energy deposit Djamel Ouerdane - Niels Bohr Institute

  8. Tracks reconstructed in Tracking Chambers (TPCs and DCs) Matched in the magnet gap Tracking in the Spectrometers Bending of tracks  momentum of particles (p = qB) Djamel Ouerdane - Niels Bohr Institute

  9. How does a real event look ? T2 Front-Forward Spectrometer D2 magnet gap T1 D1 magnet gap Mid-rapidity Spectrometer TPM1 D5 magnet gap TPM2 Vertex Beam Line Djamel Ouerdane - Niels Bohr Institute

  10. Time of Flight at 4.5 m [ns] Momentum [GeV/c] 125 scintillator slats Tof resolution :   100 ps K separation up to p  2 GeV/c PID with the Time-of-flight Wall TOFW (MRS) Djamel Ouerdane - Niels Bohr Institute

  11. TOF [ns] 38 Time-of-flight wall H1 (40 slats – PMT time resolution σ  65 ps) 36 C1 π threshold TOF resolution :   85 ps 34 32 Threshold Cherenkov C1 (π momentum threshold  2.7 GeV/c K momentum threshold  8.7 GeV/c) 30 -6 -4 -2 0 2 4 6 1/q momentum [GeV/c] p/K separation up to p  6 GeV/c PID in the front-forward spectrometer (FFS) Djamel Ouerdane - Niels Bohr Institute

  12. PID in the back forward spectrometer (BFS) Time-of-flight wall H2 32 scintillator slats 18 meters from nominal vertex TOF resolution:   85 ps Pion-veto by the RICH Djamel Ouerdane - Niels Bohr Institute

  13. Proton acceptance (TOFW and H1 only) Djamel Ouerdane - Niels Bohr Institute

  14. Antiparticle to Particle Ratios vs Pt and centrality in 197Au+197Au reaction at 200 GeV BRAHMS Preliminary BRAHMS Preliminary Pions  1 Pions  1 Kaons  0.92 Kaons  0.92 Protons  0.75 Protons  0.75 No sign of Pt or centrality dependence Djamel Ouerdane - Niels Bohr Institute

  15. Rapidity dependence – pions and kaons ( 200 GeV) Pions Kaons Djamel Ouerdane - Niels Bohr Institute

  16. Rapidity dependence – proton ratio ( 200 GeV) Baryon transport … or pair production? We need the yields! Djamel Ouerdane - Niels Bohr Institute

  17. Energy Systematics (y=0) Protons Kaons - towards matter-antimatter balance…. Djamel Ouerdane - Niels Bohr Institute

  18. CM Energy N(p) 26* 31 5 17 GeV 9* 20 130 GeV 29 (7)* (30) (23) 200 GeV * NA49 QM99 & Phys. Rev. Lett. 82, 2471 (1999) * PHENIX nucl-ex/0112006 * Assuming 14% more pbar (cf. dN/dη, BRAHMS sub to PRL dec.2001) and 0.75. Net protons at midrapidity Djamel Ouerdane - Niels Bohr Institute

  19. Measured , and • - for p and K this is the highest so far observed in HI collisions +  - • Strong rapidity dependence of p ratio • - consistent with high transperancy scenario • (but Bjorken limit not reached) + + Antiparticle-to-particle ratios in Au+Au at GeV • Ratios nearly independent of Pt and centrality • Strong energy dependence of p and k ratios • (towards matter-antimatter balance at RHIC) • Present models do not reproduce RHIC data Djamel Ouerdane - Niels Bohr Institute

  20. Comparison between Au+Au and p+p at 200 GeV Particle yields And more to come Djamel Ouerdane - Niels Bohr Institute

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