April 29, 2001APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute1 nReaction features in 65 AGeV Au + 65AGeV Au nElectromagnetic dissociation ndN(ch)/d.
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April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Reaction features in 65 AGeV Au + 65AGeV 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
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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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
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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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
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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BRAHMS in the 2’ hall
… in 1998
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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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
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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BRAHMS acceptanceAugust 2000
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Global detectorsSiMA, TMA, BB
SiMA (2.0< | |<2.0) PTMA (2.2< || <2.2) Beam-Beam (3 < | | < 4)
97% (geom)
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Centrality determinationVertex distribution
1m
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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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
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Neutral Energy correlations (ZDC)
C2(EL,ER)=P(EL,ER)/(P(EL)*P(ER))
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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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
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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TPC tracks, Vertex reconstruction, Charged particle track density
MTPC1
z
y
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Multiplicity of Charged Particle tracks in TPC’s
B = 0
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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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
?
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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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
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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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
22
2
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Hadron identification MRS (90, 40 deg)
m2=p2( t2 / L2 -1)
p-bar
K p
=0
=3
p
K
0
p, pbar
K±
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Hadron IdentificationFS (4 deg)
p-bar
=3
C1,H1,T2
+
p
m2=p2( t2 / L2 -1)
+
p
K+
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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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
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Bjorken limit reached for Au+Au s= 130AGeV?
ISR R803
s=23
s=63
BRAHMS-RHIC
Subm. to PRL
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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P-bar/p ratioCentrality dependence
BRAHMS
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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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
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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N(pbar)/N(p)Au+Au s= 130AGeV
BRAHMS
Subm. to PRL
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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StrangenessK-/K+ vs rapidity
Preliminary
CERN-SPS
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How consistent are the models?
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Net Baryons VERY PRELIMINARY
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Summary First Au+Au s=130 AGeV
FUTURE RHIC startup June 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
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Various EXTRA’s
Some are obsolete
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Multiplicity Fluctuationsin y and
Nch(p+p)= -4.2 + 4.69 (s)0.115
SPS: Nch(p+p)= 7.3 RHIC(130): Nch(p+p)= 17 RHIC(200): Nch(p+p)= 20 LHC : Nch(p+p)= 60
KNO scaling: <Nchq>=cq <Nch>q
cq indep. of energy =(<N2>-<N>2)/<N> indep. of
s But scales with Np
ch(p+p)=5.3
A+A: <Nch> increases with Np
Expect ch(RHIC)=5.3 (if like p+p)
Re. Heiselberg nucl-th/0003046
Wounded Nucleon model (WNM)
(no rescattering, superposition of p+p) Corrections for centrality cuts
may decrease ch
N= n+<n> Np
Cf. NA49 ch= 2.0
Thermal model (max rescattering): ch=2.2
EXPERIMENT: measure:
ch=(<N2>-<N>2)/<N> vs y, , centrality %
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Multiplicity Fluctuationsin y and
=(<N2>-<N>2)/<N>
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Multiplicity fluctuation analysis
=(<N2>-<N>2)/<N>
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Fluctuation AnalysisPreliminary (Erik Jacobsen)
y-1.8
y-0.5
y0
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Particle Identification in FS at 4 deg.
-, K-, pbar +, K+, p
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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BRAHMS acceptance and PID capability (,K)
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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p-bar/p vs y, b, pt
H
F
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Antiproton absorption in MRS
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Hyperon decays in HIJING
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Particle productionFritiof and Hijing
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Particle productionp and
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Strangeness in BRAHMSK-/K+ vs rapidity
BRAHMS Preliminary K-/K+= 0.92-0.83 30-35% increase as
compared to SPS (s=17 AGeV)
Plateau? HIJING flat FRITIOF peaked at
midrapidityCERN-SPS
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Particle production and K+
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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PionsFritiof 7.02, Hijing
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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BRAHMS Acceptance
Acceptance for charged in MRS at =0 (both signs accepted)
Acceptance in FS (august 2000)
h+
h-
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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BRAHMS TPC events
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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N(Pbar)/N(p) systematicsvs CM energy
BRAHMS
STAR
PHENIX
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Charged Particle production vs. Npart
Nch 23.5 pr. part. Pair
cf. Nch 17 in p+p at s=130GeV
(35-40% increase)
dN/d 3 (=0) pr.part pair.
Cf. HIJING, FRITIOF, UrQMD
TPC CEJ
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Charged Particle production vs. Npart
Nch 23.5 pr. part. Pair cf. Nch 17 in p+p at s=130GeV (35-40% increase) dN/d 3 (=0) pr.part pair. Cf. HIJING, FRITIOF
BRAHMS preliminary
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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dN/d (=0) vs NpartMTPC1 track counting
BRAHMS (CEJ)
April 29, 2001 APS-Wash-DC, Jens Jørgen Gaardhøje, Niels Bohr Institute
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Total charged particle
Multiplicity
BRAHMS
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Identified HadronsN(p-bar)/N(p)
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