2. Recent Results from BRAHMS from y=0 to y=3 I. G. Bearden Niels Bohr Institute University of Copenhagen, Denmark Quark Matter 2002, July 18-24, Nantes, France for the BRAHMS COLLABORATION

3. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 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

4. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 The BRAHMS Experiment 95° 30° 15° 2.3°

5. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Determination of Collision Vertex, Centrality

6. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Sys. Error : 10% 8% 0-5% 5-10% 10-20 Multiplicity density @ 200GeV 100AGeV+100 AGeV:  N(ch)d  = 4630 Central 0-5% dN(ch)/d  (  =0) =632 FWHM of distribution  = 7.5  0.5 For details, see the BRAHMS poster by S. Sanders, H. Ito.

7. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Limiting fragmentation Shift data to beam frame of reference PRL 88 (2002) 2002301 BRAHMS PLB 523 (2001) 227 BRAHMS Phys Rev C (2000)62 014903 Moving away from midrapidity particle production looks like SPS

8. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 dN ch /d  : Comparison to Models  S NN =200GeV AMPT High density QCD gluon saturation Kharzeev and Levin, PLB523(2001)79 Differences for Peripheral Collisions but Small effect !

9. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 MRS  FORWARD 

10. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 PID in BRAHMS MRS TOF FS TOF FS TOF +C1 RICH

11. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Ratios are (relatively) easy... Ratios could vary in pt, and in y Narrow y bins, look vs pt geometric acceptance same for particles and antiparticles, so correction is not needed. For given B field, angular setting, compare (+) and (-) polarity Normalize to number of triggers, and --bingo!-- ratios.... No dependence on transverse momentum or centrality See poster for details of the analysis! 4o4o 8o8o 12 o

12. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Particle/Particle vs rapidity BRAHMS, submitted to PRL 12/07/02 nucl-ex/0207006

13. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 BRAHMS, submitted to PRL 12/07/02 nucl-ex/0207006 Becattini: T=170,  s =1 PBM (PhysLettB518 (2000)41) predicts y=0 ratios almost exactly K - /K + = exp(2  s/T)(pbar/p) 1/3 K - /K + =(pbar/p) 1/4 is a fit to the data points

14. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Top 10% central K + p cross~1.2GeV/c P pion cross >2GeV/c?

15. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Not surprisingly, the antiparticle spectra don’t look much different...at y=0!

16. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 ,p cross 1.2 GeV/c p>K over covered p T Only small part of high rapidity data analyzed...so far.

17. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Pbar, K- yield lower than p, K+ Pbar,  - cross at higher p T

18. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Inverse p T Slope vs. mass... Nb: all fits are in pt, over same range for all particles, at all rapidities

19. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Strangeness : ratio K/ 

20. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 y = 3 similar to SPS Strangeness : K/  systematics

21. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002

22. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 p and pbar yields 0-10%: BRAHMS Preliminary  SNN=200 GeV: 0-10% Central y = 0 y=0.8

23. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 p and pbar at y=2.9 BRAHMS Preliminary antiproton Yield =10.5  0.8  1.6 (Inverse pt slope =325.5  17.3) proton Yield = 33.7  1.8  5.1 (Inverse pt slope = 341.8  13.8

24. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Net protons, first shot... BRAHMS Preliminary d 2 N/dp T dy

25. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Net protons vs Rapidity!

26. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Can we kill models? Points scaled by 2

27. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Q’ AMPT

28. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 High p t y=0 y=0 High p t y=2.2 C.E.Jørgensen Parallel session I today.

29. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Future plans... Analyze complete data set at high rapidity – Better pt coverage – (slightly) higher y Spectra, yields for 1<y<3 Source size at mid, forward rapidity p+p data Longer term... – Upgrades better high pt PID in MRS

30. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Summary K-/K+, pbar/p ratios fall off with rapidity Universal correlation between K-/K+ and pbar/p K-/  - decreases from 0.15 (y=0) to 0.1(y=3) Inverse slope decreases with rapidity Measured dN/dy over 3 units of rapidity. Dramatic increase in net protons at y=3  Low to high chemical potential from y=0 to y=3  Net baryon central plateau (y=0 to almost y=2)  Significant transparency

31. BRAHMS I.G.Bearden, Niels Bohr Institute 20 July 2002 Radius versus Momentum Zoom in RICH used for PID p>15GeV/c K>8 GeV/c  >4 GeV/c