1. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute1 nReaction features in 65 AGeV Au + 65 AGeV Au nElectromagnetic dissociation ndN(ch)/d  distribution -4<  <4 vs. Collision Centrality nProduction of charged particles, N(ch)/pr.participant nBjorken limit attained ? Transparency or Stopping np-bar/p vs y, b, p t nStrangeness vs y nFuture… BRAHMS Y2000 run @ RHIC:  s nn =130 GEV

2. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute2 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, 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, 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

3. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute3 RHIC physics August 2000 2:00 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 = +79 1 MeV/u Q = +32 HEP/NP  g-2 U-line BAF (NASA) BRAHMS: L peak = 3.3  10 25 cm -2 s -1 L ave = 1.7  10 25 cm -2 s -1 Rcoll= 350 Hz PHOBOS 6  b -1 2 wks

4. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute4 Virtual Tour of RHIC

5. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute5 BRAHMS in the 2’ hall … in 1998

6. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute6 Forward & Midrapidity spectrometers FS: 2 TPC, 2 TOF, C, 3 Drift Ch. Mod., RICH, 4 Dipoles 2.5 - 30 deg.  = 1.5 - 4 MRS: 2 TPC, 1 Dipole, 1TOF 30 - 90 deg.  = 0 - 1.5

7. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute7 BRAHMS acceptance August 2000

8. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute8 Global detectors SiMA, TMA, BB  SiMA (-2.0<  <2.0)  PTMA (-2.2<  <2.2)  Beam-Beam (3 < |  | < 4) 97%  (geom)

9. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute9 Simulated collision (URQMD) (b=5fm) 200GeVA

10. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute10 Centrality determination Vertex distribution 1m

11. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute11 Electromagnetic nuclear dissociation LO+NLO Mutual EM Mutual Electromagnetic dissociation (Spectrum of virtual photons) * (absorption cross section) = WW Multiphonon GDR excitation,  abs EM vs Nuclear coll. => neutron (L*R) coincidences RELDIS. Pshenichnov, JPB, IM, et al. EM dissociation selected by ZDC coincidences and TMA Veto in BRAHMS n n n 2n 1n LO NLO

12. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute12 Neutral Energy correlations (ZDC) C2(E L,E R )=P(E L,E R )/(P(E L )*P(E R ))

13. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute13 dN ch /d  SiMA, TMA, BB, TPC nN=  dE / nP(0)/P(n  1) nBackground corr.due to secondaries (20-50%) nConsistency between several independent. detector systems n  N(ch)d  = 4000±200 nCentral 0-5% dN(ch)/d  (  =0) =550 nFWHM of distribution  = 7.6  0.7 BRAHMS preliminary MTPC1 (CEJ) Yuri Blyakhman. BRAHMS Thesis

14. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute14 TPC tracks, Vertex reconstruction, Charged particle track density MTPC1 z y

15. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute15 Multiplicity of Charged Particle tracks in TPC’s B = 0

16. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute16 Total production of Charged particles n4000 charged part. observed nNch  23.5 pr. part. Pair ncf. Nch  17 in p+p at  s=130GeV n35-40% increase over p+p Syst ?

17. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute17 Centrality and Number of Participants Cent %b (fm)HIJINGFritiofGlauber 0-100-5329.2321.7316 10-205-7233.8230.0223 20-307-8.5163.3162.9154 30-408.5-10108.6111.8102 40-5010-1170.072.963

18. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute18 N Charged vs. number of participant nucleon pairs ndN/d   3 (  =0) pr.part pair. nCf. HIJING, FRITIOF nNo saturation effects observed Claus Ekman Jørgensen. BRAHMSThesis FRITIOF HIJING MTPC1 CEJ EKRT

19. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute19 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±  

20. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute20 Hadron Identification FS (4 deg)  p-bar  =3 C1,H1,T2 ++ p m 2 =p 2 ( t 2 / L 2 -1) ++ p K+

21. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute21 N(pbar)/N(p) Centrality and P t dependence nAntiproton absorbtion correction to pbar/p ratio: 5 % for FS at 4 deg 2 % for MRS at 90, 40 deg n10% corr. (low pt) p from Be-tube nApplied to data nMost pbar and p from Hyperon decays fall into spectrometer acceptance. nCorrection factor depends on H/B, H-bar/B-bar and T B /T H For H/B < 0.5 systematic correction is <  5% on ratio nModel dependent  not applied to data

22. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute22 Bjorken limit reached for Au+Au  s= 130AGeV? ISR R803  s=23  s=63 BRAHMS-RHIC Subm. to PRL

23. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute23 P-bar/p ratio Centrality dependence BRAHMS

24. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute24 N(p-bar)/N(p) systematics vs CM energy STAR PHENIX  BRAHMS

25. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute25 Strangeness K-/K+ vs rapidity BRAHMS Preliminary CERN-SPS

26. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute26 How consistent are the models?

27. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute27 Summary First Au+Au  s=130 AGeV FUTURE nRHIC startup July 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  7.6 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 nMidrapidity Plateau? ny =0,0.7,2 : pbar/p  0.64, 0.66, 0.41 (±0.05 ± 0.06) nWeak pt and centrality dependence nBjorken limit not reached nModels inconsistent with data

28. May 18, 2001Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute28 N(pbar)/N(p) Au+Au  s= 130AGeV BRAHMS Subm. to PRL