8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT Brahms: Forward Physics at RHIC T1 MTPC1 T2 MTPC2 MRS: 90 deg 6.5 msr FS: 6 deg 0.8 msr Dipole Magnets

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT 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. Jakobsen 7, A. Jipa 10, J. I. Jørdre 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. Løvhøiden 2, Z. Majka 3, A. Makeev 8, E. McBreen 1, M. Mikkelsen 12, M. Murray 8, J. Natowitz 8, B.S.Nielsen 7, J. Norris 11, K. Olchanski 1, J. Olness 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

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT MRS  FOWARD  GLOBAL

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT Global detectors Silicon Strips Plastic Scintillator Tiles BB : Provide vertex and start time for TOF (and forward multiplicity) MA : Provide multiplicity / centrality of collision

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT Multiplicity at from MA and BB BRAHMS Preliminary 4630 ± 370 charged particles produced for 0-5 % central. 21 % increase over 130 GeV dNch/dη (η=0) = 625 ± 55(syst.) 14% increase over 130 GeV. Phobos 200 GeV : PRL 88, : dNch/dη (η=0) = 650 ± 35(syst.) 200 GeV : Submitted to PRL (nucl-ex/ ) 130 GeV : Phys. Lett. B 523, p % 5-10% 10-20% 20-30% 30-40% 40-50%

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT Comparison to scaled and models data(UA5, Z. Phys. C 33, 1) : BRAHMS data shows 50% increase at η = 0 Models : Kharzeev and Levin (solid) and AMPT(dashed) describes the data well. pppp BRAHMS Preliminary

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT dN/d  vs.  BRAHMS Preliminary

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT Charged Particle Mult.  s nn =130GeV BRAHMS. Phys Lett. B (2001) SPS

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT Limiting fragmentation: SPS=>RHIC SPS Pb- Pb(NA49) 200 GeV top 5% 130 GeV top 5% 200 GeV 30-40%

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT dN/d  vs Npart Kharzeev and Levin (nucl- th/ ) Soft-Hard: dN/d  =(1-X) n pp /2 + X n pp =1049, =339, npp=2.43 =>dN/d  =668 (with X=0.9) High Density QCD-saturation: dN/dy =f(Npart,Q s 2,,  QCD,  s,y) with =0.3 from HERA data => dN/d  =620 (using dN/d  =549at  s=130GeV) Fit to dN /d  = AN + BN : chpart coll 130: A= 1.24  0.08±0.2, B = : A= 1.26  0.09±0.2 B =

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT Comparison to Kharzeev &Levin PLB523(2001)79 High dens. QCD Gluon saturation (red dashed) AMPT Zhang et al. PRC61(2001) (blue dashed) Data symmetrized Error bars are Total = Sys. + Stat.

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT dN(200GeV)/dN(130GeV) top 5% K&L solid lineAMPT dashed line

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT Ratios of particles and anti-particles at By looking at ratios of particles and anti-particles in the same spectrometer angular setting, from fields of opposite polarities the geometrical acceptance of the detector and efficiencies will tend to cancel out. We still have to take into account absorption of anti-protons and protons produced in the beampipe.

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT Ring Imaging Cherenkov 2

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT Rapidity dependence of ratios at. BRAHMS Preliminary (and feeddown) PRL 87, 2001 ▄

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT Ratios vs Pt and centrality BRAHMS Preliminary No sign of Pt or centrality dependence

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT Pbar/p increases slowly with √S

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT We don’t yet understand baryon transport AMPT

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT √S dependence, towards matter/antimatter balance ProtonsKaons Preliminary

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT Estimate of net protons at midrapidity * Assuming 14% more pbar (cf. dN/dη, BRAHMS sub to PRL dec.2001 ) and GeV (30)(23) (7) * * NA49 QM99 & Phys. Rev. Lett. 82, 2471 (1999) 17 GeV * * PHENIX nucl-ex/ GeV *9* N(p)CM Energy

8 th February 2002Michael Murray, Texas A&M, CMS Heavy Ion Mtg at MIT Summary First Au+Au  s nn =130,200 GeV RESULTS: Nch (0-5%)  5000 dN/d  (y=0)  632.  FWHM  7.5 N(ch)  30 pr. participant- pair dN/d  (y=0)  3.5/part. pair p-bar/p higher at y=0, similar at forward rapidity RESULTS: Nch (0-5%)  4000 dN/d  (y=0)  550.  FWHM  7.2 N(ch)  23 pr. participant-pair dN/d  (y=0)  3 pr. part. Pair p-bar/ p vs y shows increased but still incomplete transparency Midrapidity Plateau? y =0,0.7,2 : pbar/p  0.64, 0.66, 0.41 (±0.05 ± 0.06) Weak pt and centrality dependence Models inconsistent with data