1. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute1 nReaction features in 65 AGeV Au + 65AGeV 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. April 29, 2001APS-Wash-DC, 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. April 29, 2001APS-Wash-DC, 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. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute4 BRAHMS in the 2’ hall … in 1998

5. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute5 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

6. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute6 BRAHMS acceptance August 2000

7. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute7 Global detectors SiMA, TMA, BB  SiMA (2.0< |  |<2.0)  PTMA (2.2< |  | <2.2)  Beam-Beam (3 < |  | < 4) 97%  (geom)

8. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute8 Centrality determination Vertex distribution 1m

9. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute9 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 et al. EM dissociation selected by ZDC coincidences and TMA Veto in BRAHMS n n n 2n 1n LO NLO

10. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute10 Neutral Energy correlations (ZDC) C2(E L,E R )=P(E L,E R )/(P(E L )*P(E R ))

11. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute11 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

12. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute12 TPC tracks, Vertex reconstruction, Charged particle track density MTPC1 z y

13. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute13 Multiplicity of Charged Particle tracks in TPC’s B = 0

14. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute14 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 ?

15. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute15 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

16. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute16 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 2 2 2

17. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute17 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±  

18. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute18 Hadron Identification FS (4 deg)  p-bar  =3 C1,H1,T2 ++ p m 2 =p 2 ( t 2 / L 2 -1) ++ p K+

19. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute19 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

20. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute20 Bjorken limit reached for Au+Au  s= 130AGeV? ISR R803  s=23  s=63 BRAHMS-RHIC Subm. to PRL

21. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute21 P-bar/p ratio Centrality dependence BRAHMS

22. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute22 N(p-bar)/N(p) systematics vs CM energy STAR PHENIX  BRAHMS

23. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute23 N(pbar)/N(p) Au+Au  s= 130AGeV BRAHMS Subm. to PRL

24. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute24 Strangeness K-/K+ vs rapidity Preliminary CERN-SPS

25. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute25 How consistent are the models?

26. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute26 Net Baryons VERY PRELIMINARY

27. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute27 Summary First Au+Au  s=130 AGeV FUTURE nRHIC startup June 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. April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute28 Various EXTRA’s Some are obsolete

29. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute29 Multiplicity Fluctuations in y and  nN ch (p+p)= -4.2 + 4.69 (s) 0.115 nSPS: N ch (p+p)= 7.3 nRHIC(130):N ch (p+p)= 17 nRHIC(200):N ch (p+p)= 20 nLHC : N ch (p+p)= 60 nKNO scaling: =c q q c q indep. of energy n  =( - 2 )/ indep. of  s nBut scales with N p n   ch (p+p)=5.3 nA+A: increases with N p nExpect  ch (RHIC)=5.3 (if like p+p) nRe. Heiselberg nucl-th/0003046 nWounded Nucleon model (WNM) (no rescattering, superposition of p+p) nCorrections for centrality cuts may decrease  ch n  N =  n +  Np nCf. NA49  ch = 2.0 nThermal model (max rescattering):  ch =2.2 nEXPERIMENT: measure:  ch =( - 2 )/ vs y, , centrality %

30. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute30 Multiplicity Fluctuations in y and   =( - 2 )/

31. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute31 Multiplicity fluctuation analysis      =( - 2 )/

32. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute32 Fluctuation Analysis Preliminary ( Erik Jacobsen) y  -1.8 y  -0.5 y0

33. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute33 Particle Identification in FS at 4 deg.  -, K -, pbar  +, K +, p

34. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute34 BRAHMS acceptance and PID capability ( ,K)

35. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute35 p-bar/p vs y, b, pt H F

36. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute36 Antiproton absorption in MRS

37. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute37 Hyperon decays in HIJING

38. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute38 Particle production Fritiof and Hijing

39. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute39 Particle production p and 

40. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute40 Strangeness in BRAHMS K-/K+ vs rapidity nBRAHMS Preliminary nK-/K+= 0.92-0.83 n30-35% increase as compared to SPS (  s=17 AGeV) nPlateau? nHIJING flat nFRITIOF peaked at midrapidity CERN-SPS

41. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute41 Particle production  and K+

42. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute42 Pions Fritiof 7.02, Hijing

43. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute43 BRAHMS Acceptance nAcceptance for charged in MRS at  =0 (both signs accepted) nAcceptance in FS (august 2000) h+ h-

44. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute44 BRAHMS TPC events

45. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute45 N(Pbar)/N(p) systematics vs CM energy BRAHMS STAR PHENIX 

46. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute46 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 TPC CEJ

47. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute47 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

48. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute48 dN/d  (  =0) vs Npart MTPC1 track counting BRAHMS (CEJ)

49. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute49 Total charged particle Multiplicity BRAHMS

50. April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute50 Identified Hadrons N(p-bar)/N(p)