1. BRAHMS Y2000 + Y2001 @ RHIC: snn=130 GeV, and snn=200 GeV
Reaction features in AGeV AGeV and 100 AGeV AGeV Au-AU collisions
EM dissociation
dN(ch)/d distribution -4<< vs. Collision Centrality
Production of charged particles, N(ch)/pr.participant
Bjorken limit attained ? Transparency or Stopping
p-bar/p vs y, b, pt
Strangeness vs y
Future
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

2. BRAHMS Intl. collaboration
I.G. Bearden7, D. Beavis1, C. Besliu10, Y. Blyakhman6, J. Bondorf7, J.Brzychczyk4, B. Budick6, H. Bøggild7, C. Chasman1, C. H. Christensen7, P. Christiansen7, J.Cibor4, R.Debbe1, J. J. Gaardhøje7, K. Grotowski4, K. Hagel8, O. Hansen7, H. Heiselberg7, A. Holm7, A.K. Holme12, H. Ito11, E. Jacobsen7, A. Jipa10, J. I. Jordre10, F. Jundt2, C. E. Jørgensen7, T. Keutgen9, E. J. Kim5, T. Kozik3, T.M.Larsen12, J. H. Lee1, Y. K.Lee5, G. Løvhøjden2, Z. Majka3, A. Makeev8, B. McBreen1, M. Murray8, J. Natowitz8, B.S.Nielsen7, K. Olchanski1, D. Ouerdane7, R.Planeta4, F. Rami2, D. Roehrich9, B. H. Samset12, S. J. Sanders11, I. S. Sgura10, R.A.Sheetz1, Z.Sosin3, P. Staszel7, T.S. Tveter12, F.Videbæk1, R. Wada8 and A.Wieloch3.
1Brookhaven National Laboratory, USA IReS and Université Louis Pasteur, Strasbourg, France Jagiellonian University, Cracow, Poland Institute of Nuclear Physics, Cracow, Poland Johns Hopkins University, Baltimore, USA New York University, USA Niels Bohr Institute, Blegdamsvej 17, University of Copenhagen, Denmark Texas A&M University, College Station. USA University of Bergen, Norway University of Bucharest, Romania University of Kansas, Lawrence,USA University of Oslo Norway
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

3. RHIC physics August 2000 & August 2001
BRAHMS: Lpeak = 3.3  1025 cm-2 s-1
Lave = 1.7  cm-2 s-1
Rcoll= 350 Hz
2:00 o’clock
PHOBOS
10:00 o’clock
RHIC
PHENIX
8:00 o’clock
STAR
4:00 o’clock
6:00 o’clock
6 b-1
U-line
9 GeV/u
Q = +79
BAF (NASA)
m g-2
LINAC
BOOSTER
2 wks
AGS
HEP/NP
1 MeV/u
Q = +32
TANDEMS
August 2000 and 2001
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

4. Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute
BRAHMS in the 2’ hall … in 1998
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

5. Forward & Midrapidity spectrometers
MRS: 2 TPC, 1 Dipole, 1TOF
deg =
FS: 2 TPC, 2 TOF, C1-threshold, 3 Drift Ch. Mod., RICH, 4 Dipoles
deg.  =
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

6. First BRAHMS collision at 100 AGeV+100AGeV
FS: 6 deg
0.8 msr T1
MRS: 90 deg
6.5 msr
MTPC1
MTPC2
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

7. BRAHMS acceptance August 2000 & 2001
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

8. Global detectors SiMA, TMA, BB
97% (geom)
 SiMA (-2.0< <2.0)
 PTMA (-2.2<  <2.2)
 Beam-Beam (3 < | | < 4)
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

9. Centrality determination Vertex distribution
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

10. Electromagnetic nuclear dissociation
EM dissociation selected by ZDC coincidences
and TMA Veto in BRAHMS n
LO+NLO Mutual EM
NLO
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. 2n LO
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

11. Neutral Energy correlations (ZDC)
C2(EL,ER)=P(EL,ER)/(P(EL)*P(ER))
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

12. dNch/d @ snn= 130 GeV SiMA, TMA, BB, TPC
BRAHMS Subm. Phys. Lett. B 7/2001.
N=dE /<dE>
P(0)/P(n1)
Background corr.due to secondaries (37-50%)
Consistency between 4 independent detector systems
65 AGeV+ 65 AGeV:
 N(ch)d= 4050±300
Central 0-5%
dN(ch)/d (=0) =550
FWHM of distribution
= 7.6  0.7
600
0-5%
5-10%
10-20%
20-30%
30-40%
40-50%
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

13. TPC tracks, Vertex reconstruction, Charged particle track densityz
MTPC1
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

14. Charged Particle Mult. snn=130 GeV
SPS
BRAHMS. Subm. to Phys Lett. B. 2001
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

15. NCharged vs. number of participant nucleon pairs. snn=130AGeV
FRITIOF
EKRT
HIJING
MTPC1 CEJ
Claus Ekman Jørgensen.
Thesis NBI 2001
dN/d 3 (=0) pr.part pair.
Cf. HIJING, FRITIOF
No saturation effects observed
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

16. RHIC: 200 AGeV Will this happen?
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

17. Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute
dNch/d for 100 AGeV AGeV
BRAHMS 200AGEV
100 AGeV AGeV
Au+Au
 N(ch)d= 5100±300
Central 0-6%
dN(ch)/d (=0) =61050
FWHM of distribution
= 7.9  1.0
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

18. Hard and Soft vs. High Density QCD @ 200 AGeV
Kharzeev and Levin (nucl-th/ )
Soft-Hard:
dN/d=(1-X) npp <Npart>/2
+ X npp <Ncoll>
<Ncoll>=1049, <Npart>=339, npp=2.43 =>dN/d=668 (with X=0.9)
High Density QCD-saturation:
dN/dy =
f( Npart, Qs2, ,QCD,s,y)
with =0.3 from HERA data
=> dN/d=620
(using dN/d=549 at s=130GeV)
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

19. Total production of Charged particles
BRAHMS
200 AGeV ?
130AGeV
Syst
130 AGeV
4000 charged part. observed
Nch  23.5 pr. part. pair
cf. Nch  17 in p+p at s=130GeV
35-40% increase over p+p
200 AGeV
5100 charged part. observed
Nch  30 pr. part. pair
cf. Nch  20 in p+p at s=200GeV
50% increase over p+p
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

20. Hadron identification MRS (90, 40 deg) K p
0  K±
p-bar
=3
p, pbar
=0 p K 
m2=p2( t2 / L2 -1)
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

21. Hadron Identification FS (4 deg & 130AGeV)
=3
p-bar
C1,H1,T2
m2=p2( t2 / L2 -1) + p p K+ +
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

22. N(pbar)/N(p) @ 130 AGeV Centrality and Pt dependence
Antiproton absorbtion correction to pbar/p ratio:
5 % for FS at 4 deg
2 % for MRS at 90, 40 deg
10% corr. (low pt) p from Be-tube
Applied to data
Most pbar and p from Hyperon decays fall into spectrometer acceptance.
Correction factor depends on H/B, H-bar/B-bar and TB/TH
For H/B < 0.5 systematic correction is <  5% on ratio
Model dependent  not applied to data
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

23. Bjorken limit reached for Au+Au snn= 130GeV?
ISR R803
s=63
s=23
BRAHMS
PRL sept. 2001
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

24. FS Hadron identification for snn = 200 GeV Au+Au
TOF and Cherenkov veto in FFS
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

25. Particle ratios snn = 200 GeV (y=2)K- p-
Y=2 : p-bar/p = 0.48  0.08
-/+= 0.98  0.04
BRAHMS: Preliminary
Integrated over centrality and pt range K+ p
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

26. Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute
N(p-bar)/N(p) systematics vs CM energy
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

27. Strangeness K-/K+ vs y @ snn= 130GeV
CERN-SPS
BRAHMS Preliminary
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

28. How consistent are the models @ snn= 130GeV?
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute

29. Summary: First Au+Au snn=130 & 200 GeV
RESULTS: 65+65
Nch (0-5%)  4000
dN/d (y=0)  550. FWHM  7.6
N(ch)  23 pr. participant-pair
dN/d (y=0)  3 pr. part. Pair
AntiMeson/Meson close to unity
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
Bjorken limit not reached
Models inconsistent with data
RESULTS:
Nch (0-5%)  5100
dN/d (y=0)  625. FWHM  7.8
N(ch)  30 pr. participant-pair
dN/d (y=0)  3.6 pr. part. Pair
p-bar/p = 0.48 (y=2)
Moderate growth in baryon poor ’plateau’.
Total mult. Increases by 25%,
Central mult increases by 14%
Pbar/p increases by 17% (y=2)
Large y and pt coverage to come
Sept 4, 2001
Paris, Jens Jørgen Gaardhøje, Niels Bohr Institute