results from brahms experiment at rhic pawel staszel niels bohr institute for the brahms...
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![Page 1: Results from BRAHMS experiment at RHIC Pawel Staszel Niels Bohr Institute for the BRAHMS Collaboration](https://reader036.vdocuments.us/reader036/viewer/2022062404/551a83215503466b3a8b48b5/html5/thumbnails/1.jpg)
Results from BRAHMS experiment at RHIC
Pawel Staszel
Niels Bohr Institute
for the BRAHMS Collaboration
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Cracow Epiphany Conference, Pawel Staszel, Niels Bohr Institute 2
I.G. Bearden7, D. Beavis1, C. Besliu10, Y. Blyakhman6, J.Brzychczyk4, B. Budick6, H. Bøggild7, C. Chasman1, C. H. Christensen7,
P. Christiansen7,J.Cibor4, R.Debbe1, J. J. Gaardhøje7,M. Germinario7 ,K. Grotowski4, K. Hagel8, O. Hansen7, 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.Videb₣k1, R.
Wada8 and A.Wieloch3. 1Brookhaven National Laboratory, USA 2IReS and Universit₫ 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, 12University of Oslo Norway
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Cracow Epiphany Conference, Pawel Staszel, Niels Bohr Institute 3
1 MeV/uQ = +32
9 MeV/uQ = +79
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BRAHMS DETECTOR
FS: 1< <3.6h
GLOBAL
MRS: -0.5<?<1
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Global Detectors:SiMA, PTMA, BBC
SiMA 25 wafers segm. into 7 strips, ø=5.3cm, -2.0 < h < 2.0
PTMA 38 tiles, ø=13.9cm, -2.2 < h < 2.2 (-3<h<3)
BBC L=2.15m, st=65ps => sz ~1.0cm, 3 < |h| < 4.0 (2.1<|h|<4.7)
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Centrality determination,Vertex distribution 1m
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TPC tracks =>Vertex reconstruction and dNch/dh
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Charged particle pseudorapidity density
0-5%
5-10%
10-20%
20-30%
30-40%
40-50%
N=SdE /<dE> N=ADC/ADC(sing. part.) Background corr.due to
secondaries: 6-25%(SiMA), 20-40%(TMA), 37-50%(BB)
Consistency between 4 independent. detector systems: SiMA, TMA, BB, and TPC.
65 AGeV+65 AGeV: ò N(ch)dh= 3860±300 Central 0-5% dN(ch)/dh (h=0) =550 FWHM of distribution
Dh= 7.2 ± 0.8
BRAHMS Phys. Lett. B 523 (2001) 227; nucl-ex 0108016
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9
dNch/dh @ 200GeV
p`p
4630 ± 370 charged particles produced for 0-5% central 20% increase over 130GeV
Dh= 7.5± 0.5 dN(ch)/dh (h=0) =625, 14% increase over 130
GeV »50% increase over p+ pbar (UA5) => significant medium effects
—
BRAHMS @ 200
Bjorken energy density
eBJ = (1/pR2t0) d<Et>/dh ³ 5 GeV/fm3
(d < Et>=dN * <pt> , t0=1fm/c,
R»6fm, <pt> = 0.5GeV/c)
cf: eQGPcritical » 1 GeV/fm3
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Saturation of excitation in fragmentation region: SPS=>RHIC
BRAHMS subm. to PRL- nuc-ex. 00112001
Shift data to beam frame of reference
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dN/dh vs Npart
Kharzeev and Levin (nucl-th/0108006)
Soft-Hard:
dN/dh = (1-X) npp <Npart>/2 + X npp<Ncoll>
<Ncoll>=1049, <Npart>=339, npp=2.43
=>dN/dh=668 (with X=0.12)
High Density QCD-saturation:
dN/dy =f(Npart,Qs2,l,LQCD,Ös,y)
with l=0.25÷0.3 from HERA data
=> dN/dh=616÷634
(using dN/dh=549 at Ös=130GeV)
h=0
h=4.5
h=3
130: A= 0.97 ± 0.08, B =0.22 ±0.04
200: A= 1.12 ± 0.1, B =0.24 ±0.04
Fit to dNch/dh = Anpart + BNcoll:
36÷37% of hard component}(h=0)
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dNch(200GeV)/dNch(130GeV)AMPT dashed line K&L solid line
0-5% 5-10%
30-40% 40-50%
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BRAHMS Spectrometer
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Back Forward Platform
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Acceptance and Hadron Identification
BRAHMS has large acceptance for identifiedparticles, up to y~4 for p and 3.5 for p. In MRS: PID via TOF vs mom.p separation upto~3GeV/c.
In FS: TOF1,C1, TOF2,RICH in various combinations
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Proton and Kaon data
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Hadron Identification: MRS (90-40deg), TOF
m2 = p2(t2/L2 –1)
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Hadron Identification: FS (3-20deg), TOF
p+
p
K+
4 deg
C1
H1 T2
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Hadron Identification:FS (3-20deg), TOF and C1
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Ring Imaging Cherenkov for high momentum PID
´
q Þ R
p>15GeV/c
K>8 GeV/c
p>4 GeV/c
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N(pbar)/N(p) @ 130 AGeV Centrality and Pt dependence
Antiproton absorbtion correction to p-bar/p ratio: 5 % for FS at 4 deg, 2 % for MRS at 90 and 40 deg. Proton production (? and Be–tube): 10% and 6% (low Pt bin) for MRS at 90 and 40 deg., respectively. Hyperon decays: p-bar/p » anti-hyperon/hiperon then weak-decay would not affect p-bar/p ratio. Fritiof 7.02 + GEANT Þsystematic correction is < 5%. Model dependent Þ not aplied to data.
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Antiparticle/particle ratios vs Pt @ 200GeV, (y=0)
BRAHMS Perliminary
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Antiparticle/particle ratios @ 200GeV
p-/p = p-(pair) / [p+p(pair)]
K-/K+ = K-(pair) / [K+(pair)+K+(ap)]
(p+p ® p+L+K+)
p+p- pair prod (& ch. exch).
Midrapidity: near matter-antimatter balance
BRAHMS Perliminary
”+” » ”-
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How consistent are models?BRAHMS PRL 87(2001)112305, nucl-ex/0106011
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N(p-bar)/N(p) systematics
130GeV
200 GeV
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Summary First Au+Au Ösnn=130, 200 GeV
dN/dh(y=0) = 550, Nch(0-5%) = 3860, DhFWHN»7.2,
Nch/0.5<Npart> » 22,
dNch/dh(h=0) » 3.1 pr. part. Pair, p-bar/p vs y shows increase but still
incomplete transparency p-bar/p » 0.64, 0.66, 0.41 at y=0, 0.7, 2,
respectively Weak Pt and centrality dependence, Models inconsistent with data
dN/dh(h=0) = 625, dNch/dh(h=0) » 3.7 pr. part. pair, Nch(0-5%) = 4630, DhFWHN»7.5, Nch/0.5Npart » 28, p-bar/p vs y shows increase but still
incomplete transparency p-bar/p higher at mid- and central rapidity.
RESULTS: 65+65 RESULTS: 100+100
Large energy density > 5 ecrit
Decoupling of central and fragmentation regions
Partonic (color) description appears necessary
Central region dominated by
matter-antimatter balance: Þ Qualitatively new physics regime
To come: particle spectra, Strangeness,
net baryon density,
jet quenching,...