2. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute1 n100 AGeV + 100 AGeV Au+Au Ecm =  s  40 TeV THE LITTLE BIG BANG and search for Quark Gluon Plasma. n  5000 charged hadrons produced per central Au + Au collision. nNuclear Transparency, Bjorken boost invariant plateau? nTowards nuclear ’stuff’ with matter-antimatter balance nEquilibrated matter ? nHigh pt suppression, the smoking gun of QGP? BRAHMS at RHIC Au+Au, d+Au @  s nn =200 GeV

3. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute2 NIM, A499 (2003) 437

4. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute3 BRAHMS: The forward experiment FS: TPC, TOF, Cherenkov 2.5 - 30 deg.  = 1.5 - 4 MRS: TPC, TOF 30 - 90 deg.  = 0 - 1.5 Global: |  | < 5

5. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute4 I.G. Bearden 7, D. Beavis 1, C. Besliu 10, Y. Blyakhman 6, J. Bondorf 7, 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, J. J. Gaardhøje 7, M. Germinario 7, K. Grotowski 4, K. Hagel 8, O. Hansen 7, H. Heiselberg 7, A. Holm 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, 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. 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, S. J. Sanders 11, D. Sandberg 7,I. S. Sgura 10, R.A.Sheetz 1, Z.Sosin 3, P. Staszel 7, T.S. Tveter 12, F.Videbæk 1, R. Wada 8 and A.Wieloch 3. 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 BRAHMS Intl. collaboration

6. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute5 Excellent Hadron ID by TOF and RICH m 2 =p 2 ( t 2 / L 2 -1) D p  K DD

7. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute6 BRAHMS acceptance Many fields and angles …

8. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute7 Hadron spectra vs. Pt, rapidity and centrality a sample of Djamels spectra vs y f. eks pions.

9. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute8 Stopping, transparency, & boost invariance y dN/dy 0y 0 y 0

10. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute9 Stopping or transparency at RHIC ?

11. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute10 Net Proton yield for Au+Au at  s nn =200 GeV Net protons = N(p)-N(anti-p) A measure of the baryon transport Central (Bjorken) Plateau ? Observed protons: only part of the story. Corrections needed for other hadrons (n, , , etc…)

12. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute11 Transparency at RHIC Relative rapidity loss : 32% <  y < 48% Transparency but still a large transfer of kinetic energy to excitations (of the color field) Peter Christiansen Ph. D. thesis, NBI, June 2003

13. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute12 Do models describe reaction mechanism at RHIC? Hijing: (Partonic, Strings, no rescattering) UrQMD: Hadronic, Transport calc, resonance excita. rescattering Data corrected for p feed down from hyperons

14. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute13 Antiparticle/particle ratios @ 200AgeV ’+’  ’-’ p - /p = p - (pair) / [p+p(pair)] K - /K + = K - (pair) / [K + (pair)+K + (dir)] (p+p  p+  +K + )  +  - pair prod (& ch. exch). Midrapidity: near matter-antimatter balance ++ Boost Invariant Plateau ?! BRAHMS130 PRL 87 (2001) 202301 BRAHMS200 PRL 90 (2003) 112305.

15. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute14 Quark chemistry Chemical equilibrium? nGrand Canonical Ensemble with Strangeness and charge conservation  (p - )/  (p + )= exp(-6  u,d /T)  (K - )/  (K + )= exp(-2[  u,d -  s ]/T) = exp(2  s /T) [  (p - )/  (p + )] 1/3 nUniversal relationship between  u,d &  s nChemical equilibration for different rapidity slices? BRAHMS200 PRL 90 (2003) 112305.

16. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute15 Phase diagram of nuclear matter Lowest baryo- chemical potential yet measured in NN collisions HG

17. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute16 Charged particle multiplicity @ 200 AGeV n4630 charged particles produced for 0-5% central n14% increase over 130GeV n50% increase over p +  p (UA5) => significant medium effects Brahms 200 pppp

18. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute17 Saturation of excitations in fragmentation region Shift data to beam frame of reference BRAHMS PRL 88 (2002) 202301

19. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute18 Multiplicity,, B2(V)  energy density Bjorken energy density  = (1/  R 2  0 ) dE t /d  dE t =dN  5 GeV/fm 3 cf:  QGP critical  1 GeV/fm 3

20. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute19 4  yields of charged mesons.

21. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute20 Strangeness Production vs. CM energy K + /   =(u  s) / (u  d) K - /  - =(  u s) /(  u d) p + p  p +  + K +

22. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute21 Universal correlation of Charged kaon vs pion? Djamel Ouerdane, Ph. D. thesis, NBI, 2003. NPA715 (2003) 478

23. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute22 High pt suppression & Jet quenching at RHIC? q q q q SPS (  s nn =17 GeV) High p_t enhancement when compared to p+p scaled by N_binary: flow and quark mult scattering

24. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute23 Jet Quenching? High pt yield suppression.

25. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute24 Jet quenching Does it persist at fwd. rapidity? Analysis by Claus E. Jørgensen, NBI (QM2002: NPA) See parrallel session talk this afternoon y=2.2 BRAHMS preliminary

26. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute25 Absence of high pt suppression for d+Au ! q q Au D D+Au,  s nn =200GeV BRAHMS preliminary y=0 See Claus Jørgensen’s talk!

27. June 17, 2003NN2003, Moscow, Jens Jørgen Gaardhøje, Niels Bohr Institute26 Summary and conclusions Central region near baryon-free. Evidence for boost invariant and central plateau (|y|<2) Near matter-antimatter balance Largest energy density yet seen Consistency with thermal models over |y|=2 High pt suppression, seen at y=0,2, not seen in d+Au (y=0)