March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute1 nReaction features in 65 AGeV Au + 65AGeV Au ndN(ch)/d  distribution -4<  <4 vs. Collision Centrality nTotal production of charged particles nProduction of particles pr. participant nBjorken limit attained ? Tranparency or Stopping nP-bar/p vs y, b, p t nFuture… Results from Y2000 RHIC:  s nn =130AGEV

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute2 I.G. Bearden 7, D. Beavis 1, Y. Blyakhman 6, J. Bondorf 7, J.Brzychczyk 4, B. Budick 6, H. Bøggild 7, C. Chasman 1, P. Christiansen 7, J.Cibor 4, R.Debbe 1, J. J. Gaardhøje 7, K.Grotowski 4, J. I. Jordre 10, F. Jundt 3, K. Hagel 8, O. Hansen 7, H.Heiselberg 7, A. Holm 7, C. H. Christensen 7, A.K. Holme 2, H. Ito 9, E. Jacobsen 7, A. Jipa 11, C. E. Jørgensen 7, E. J. Kim 5, T.Kreutgel 4, T. Kozik 4, T.M.Larsen 2, J. H. Lee 1, Y. K.Lee 5, G. Løvhøjden 2, Z. Majka 4, 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 3, D. Roehrich 9, B. Samset 2, S. Sanders 9, I. S. Sgura 11, R.A.Sheetz 1, Z.Sosin 4, P. Staszel 7, T.S. Tveter 2, F.Videbæk 1, R. Wada 8 and A.Wieloch 4. 1 Brookhaven National Laboratory, USA 2 Fysisk Institutt, University of Oslo Norway 3 IReS, Université Louis Pasteur, Strasbourg, France 4 Jagiellonian University, 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 Kansas, USA. 10 University of Bergen, Norway 11 University of Bucharest, Romania BRAHMS Intl. collaboration

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute3 RHIC physics August :00 o’clock 4:00 o’clock 6:00 o’clock 8:00 o’clock 10:00 o’clock STAR PHENIX RHIC AGS LINAC BOOSTER TANDEMS 9 GeV/u Q = MeV/u Q = +32 HEP/NP  g-2 U-line BAF (NASA) BRAHMS: L peak = 3.3  cm -2 s -1 L ave = 1.7  cm -2 s -1 Rcoll= 350 Hz PHOBOS 6  b -1 2 wks

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute4 Forward & Midrapidity spectrometers FS: 2 TPC, 2 TOF, C, 3 Drift Ch. Mod., RICH, 4 Dipoles deg.  = MRS: 2 TPC, 1 Dipole, 1TOF deg.  =

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute5 BRAHMS acceptance August 2000

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute6 Global detectors SiMA, TMA, BB  SiMA (2.2< |  |<2.2)  PTMA (2.2< |  | <2.2)  Beam-Beam (3 < |  | < 4) 97%  (geom)

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute7 Centrality determination Vertex distribution 1m

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute8 TPC tracks, Vertex reconstruction, Charged particle track density MTPC1 z y

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute9 dN/d  (charged) SiMA, TMA, BB, TPC nN=  dE / nP(0)/P(n  1) nBackground corr.due to secondaries (30-50%) nConsistency betwqen several independent. detector systems n  N(ch)d  = 4020±150 nCentral 0-5% dN(ch)/d  (  =0) =550 nFWHM of distribution  = 7.6  0.7 BRAHMS preliminary MTPC1 (CEJ)

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute10 Charged Particle production vs. Npart nNch  23.5 pr. part. Pair cf. Nch  17 in p+p at  s=130GeV n(35-40% increase) ndN/d   3 (  =0) pr.part pair. nCf. HIJING, FRITIOF BRAHMS preliminary

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute11 Hadron identification MRS (90, 40 deg) m 2 =p 2 ( t 2 / L 2 -1) p-bar  KK p  =0  =3 p K  0 p, pbar K±  

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute12 Hadron Identification FS (4 deg)  p-bar  =3 C1,H1,T2 ++ p m 2 =p 2 ( t 2 / L 2 -1) ++ p K+

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute13 N(pbar)/N(p) Centrality and P t dependence nAntiproton absorbtion correction to pbar/p ratio: n9.5 % for FS at 4 deg n3 % for MRS at 90, 40 deg nApplied to data nMost pbar and p from Hyperon decays fall into spectrometer acceptance. nCorrection factor depends on nH/B, H-bar/B-bar and T B /T H nFor H/B < 0.5 systematic correction is <  0.5% on ratio nModel dependent  not applied to data

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute14 Bjorken limit reached for Au+Au  s= 130AGeV? ISR R803 BRAHMS-RHIC To be Subm. to PRL

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute15 N(pbar)/N(p) Au+Au  s= 130AGeV BRAHMS To be Subm. to PRL

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute16 How consistent are the models?

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute17 Model predictions: FRITIOF 7.02 and HIJING

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute18 Summary First Au+Au  s=130 AGeV FUTURE nRHIC startup May 2001 nAu+Au  s=200 AGeV nHigher Luminosity nNarrower vertex distribution np + p running nBRAHMS full forward spectrometer ready nStart full scan  =0 to  =4 nHigh pt coverage (PID in FS to p>25 GeV/c) RESULTS nNch (0-5%)  4000 ndN/d  (y=0)  550.  FWHM  7 nN(ch)  23 pr. participant-pair ndN/d  (y=0)  3 pr. part. pair nAntiMeson/Meson close to unity np-bar/ p vs y shows increased but still incomplete transparency ny =0,2 : N(pbar)/N(p)  62%,44% nWeak pt and centrality dependence nBjorken limit not reached nModels inconsistent with data

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute19 dN/d  (  =0) vs Npart MTPC1 track counting BRAHMS (CEJ)

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute20 Particle Identification in FS at 4 deg.  -, K -, pbar  +, K +, p

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute21 BRAHMS Acceptance nAcceptance for charged in MRS at  =0 (both signs accepted) nAcceptance in FS (august 2000) h+ h-

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute22 Total charged particle Multiplicity BRAHMS

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute23 Pions Fritiof 7.02, Hijing

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute24 Charged Particle production vs. Npart nNch  23.5 pr. part. Pair ncf. Nch  17 in p+p at  s=130GeV n(35-40% increase) ndN/d   3 (  =0) pr.part pair. nCf. HIJING, FRITIOF, UrQMD

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute25

March 19, 2001 Moriond Jens Jørgen Gaardhøje, Niels Bohr Institute26