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May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
1
Reaction features in 65 AGeV Au + 65 AGeV Au
Electromagnetic dissociation dN(ch)/d distribution -
4<<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…
BRAHMS Y2000 run @ RHIC: snn=130 GEV
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
2
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 2IReS and Université Louis Pasteur, Strasbourg, France
3Jagiellonian University, Cracow, Poland 4Institute of Nuclear Physics, Cracow, Poland 5Johns Hopkins University, Baltimore, USA
6New York University, USA 7Niels Bohr Institute, Blegdamsvej 17, University of Copenhagen, Denmark 8Texas A&M University, College Station. USA
9University of Bergen, Norway 10University of Bucharest, Romania
11University of Kansas, Lawrence,USA 12 University of Oslo Norway
BRAHMS Intl. collaboration
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
3
RHIC physicsAugust 2000
2:00 o’clock
4:00 o’clock6:00 o’clock
8:00 o’clock
10:00 o’clock
STARPHENIX
RHIC
AGS
LINACBOOSTER
TANDEMS
9 GeV/uQ = +79
1 MeV/uQ = +32
HEP/NP
g-2
U-lineBAF (NASA)
BRAHMS: Lpeak = 3.3 1025 cm-2 s-1
Lave = 1.7 1025 cm-2 s-1
Rcoll= 350 HzPHOBOS
6 b-1
2 wks
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
4
Virtual Tour of RHIC
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
5
BRAHMS in the 2’ hall
… in 1998
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
6
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
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
7
BRAHMS acceptanceAugust 2000
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
8
Global detectorsSiMA, TMA, BB
SiMA (-2.0< <2.0) PTMA (-2.2< <2.2) Beam-Beam (3 < | | < 4)
97% (geom)
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
9
Simulated collision (URQMD) (b=5fm) 200GeVA
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
10
Centrality determinationVertex distribution
1m
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
11
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
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
12
Neutral Energy correlations (ZDC)
C2(EL,ER)=P(EL,ER)/(P(EL)*P(ER))
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
13
dNch/dSiMA, TMA, BB, TPC
N=dE /<dE> P(0)/P(n1) Background corr.due
to secondaries (20-50%)
Consistency between several independent. detector systems
N(ch)d= 4000±200 Central 0-5% dN(ch)/d (=0) =550 FWHM of distribution
= 7.6 0.7
BRAHMS preliminary
MTPC1 (CEJ)
Yuri Blyakhman. BRAHMS Thesis
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
14
TPC tracks, Vertex reconstruction, Charged particle track density
MTPC1
z
y
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
15
Multiplicity of Charged Particle tracks in TPC’s
B = 0
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
16
Total production of Charged particles
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
Syst
?
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
17
Centrality and Number of Participants
Cent %
b (fm) HIJING Fritiof
Glauber
0-10 0-5 329.2 321.7 316
10-20 5-7 233.8 230.0 223
20-30 7-8.5 163.3 162.9 154
30-40 8.5-10 108.6 111.8 102
40-50 10-11 70.0 72.9 63
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
18
NCharged vs. number of participant nucleon pairs
dN/d 3 (=0) pr.part pair. Cf. HIJING, FRITIOF No saturation effects
observed
Claus Ekman Jørgensen.
BRAHMSThesis
FRITIOF
HIJING
MTPC1 CEJ
EKRT
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
19
Hadron identification MRS (90, 40 deg)
m2=p2( t2 / L2 -1)
p-bar
K p
=0
=3
p
K
0
p, pbar
K±
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
20
Hadron IdentificationFS (4 deg)
p-bar
=3
C1,H1,T2
+
p
m2=p2( t2 / L2 -1)
+
p
K+
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
21
N(pbar)/N(p)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
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
22
Bjorken limit reached for Au+Au s= 130AGeV?
ISR R803
s=23
s=63
BRAHMS-RHIC
Subm. to PRL
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
23
P-bar/p ratioCentrality dependence
BRAHMS
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
24
N(p-bar)/N(p) systematics vs CM energy
0,00
2,00
4,00
6,00
8,00
10,00
12,00
0,0 0,5 1,0 1,5 2,0 2,5
rapidity y
RH
IC/S
PS
STAR
PHENIX
BRAHMS
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
25
StrangenessK-/K+ vs rapidity
BRAHMS Preliminary
CERN-SPS
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
26
How consistent are the models?
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
27
Summary First Au+Au s=130 AGeV
FUTURE RHIC startup July 2001 Au+Au s=200 AGeV Higher Luminosity Narrower vertex distribution p + p running
BRAHMS full forward spectrometer ready
Start full scan =0 to =4 High pt coverage (PID in FS to
p=25 GeV/c)
RESULTS 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
May 18, 2001 Hard-Probes, Jens Jørgen Gaardhøje, Niels Bohr Institute
28
N(pbar)/N(p)Au+Au s= 130AGeV
BRAHMS
Subm. to PRL