Post on 24-Jan-2016
description
Brahms: Forward Physics at RHIC
T1
MTPC1
T2
MTPC2
MRS: 90 deg
6.5 msr
FS: 6 deg
0.8 msr
Dipole Magnets
The BRAHMS CollaborationI.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,
E. Enger12, J. J. Gaardhøje7, M. Germinario7 , K. Grotowski4, K. Hagel8, O. Hansen7, A.K. Holme12, H. Ito11, E. Jakobsen7, A. Jipa10, J. I. Jørdre10, F. Jundt2, C.E.Jørgensen7,
R. Karabowicz4, T. Keutgen9, E. J. Kim5, T. Kozik3, T.M.Larsen12, J. H. Lee1, Y. K.Lee5, G. Løvhøiden2, Z. Majka3, A. Makeev8, E. McBreen1, M. Mikkelsen12, M. Murray8, J. Natowitz8,
B.S.Nielsen7, J. Norris11, K. Olchanski1, J. Olness1, D. Ouerdane7, R.Planeta4, F. Rami2, D. Roehrich9, B. H. Samset12, D. Sandberg7, S. J. Sanders11, R.A.Sheetz1,
Z.Sosin3, P. Staszel7, T.S. Tveter12, F.Videbæk1, R. Wada8, A.Wieloch3, and I. S. Zgura10
1Brookhaven National Laboratory, USA, 2IReS and Université Louis Pasteur, Strasbourg, France3Jagiellonian University, Cracow, Poland, 4Institute of Nuclear Physics, Cracow, Poland
5Johns Hopkins University, Baltimore, USA, 6New York University, USA7Niels 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
MRS
FOWARD
GLOBAL
Global detectors
Silicon Strips
Plastic Scintillator Tiles
BB : Provide vertex and start time for TOF (and forward multiplicity)
MA : Provide multiplicity / centrality of collision
Multiplicity at from MA and BB200NNsBRAHMS Preliminary
4630 ± 370 charged particles produced for 0-5 % central. 21 % increase over 130 GeV
dNch/dη (η=0) = 625 ± 55(syst.) 14% increase over 130 GeV.
Phobos 200 GeV : PRL 88, 22302 : dNch/dη (η=0) = 650 ± 35(syst.)
200 GeV : Submitted to PRL(nucl-ex/0112001)130 GeV : Phys. Lett. B 523, p. 227
0-5%
5-10%
10-20% 20-30%
30-40% 40-50%
Comparison to scaled and modelspp
data(UA5, Z. Phys. C 33, 1) : BRAHMS data shows 50% increase at η = 0
Models : Kharzeev and Levin (solid) and AMPT(dashed) describes the data well.
pp
pp
BRAHMS Preliminary
dN/d vs.
BRAHMSPreliminary
Charged Particle Mult.snn=130GeV
BRAHMS. Phys Lett. B. 523 227 (2001)
SPS
Limiting fragmentation: SPS=>RHIC
SPS Pb- Pb(NA49)
200 GeV top 5%
130 GeV top 5%
200 GeV 30-40%
dN/d vs Npart•Kharzeev and Levin (nucl-th/0108006)
•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=549ats=130GeV)
Fit to dN /d = AN + BN :ch part coll
130: A= 1.24 0.08±0.2, B =0.12-+0.04-+0.06200: A= 1.26 0.09±0.2 B =0.15-+0.04-+0.05
Comparison to Kharzeev &LevinPLB523(2001)79High dens. QCD Gluon saturation (red dashed)AMPTZhang et al. PRC61(2001)067901(blue dashed)
Data symmetrizedError bars are Total = Sys. + Stat.
dN(200GeV)/dN(130GeV)
top 5% 5-10
40-5030-40
K&L solid lineAMPT dashed line
Ratios of particles and anti-particles at 200NNs
By looking at ratios of particles and anti-particles in the same spectrometer angular setting, from fields of opposite polarities the geometrical acceptance of the detector and efficiencies will tend to cancel out.
We still have to take into account absorption of anti-protons and protons produced in the beampipe.
Ring Imaging Cherenkov
2
Rapidity dependence of ratios at .
)()(
)(
)(
)(
tp
p
pNpN
pN
pN
pN
)(
)()(
)(
)(
)(
Kppp
KNKN
KN
KN
KN
app
p
BRAHMS Preliminary
(and feeddown)
PRL 87, 2001 ▄
200NNs
Ratios vs Pt and centrality
BRAHMS Preliminary BRAHMS Preliminary
No sign of Pt or centrality dependence
Pbar/p increases slowly with √S
We don’t yet understand baryon transport
AMPT
√S dependence, towards matter/antimatter balance
Protons Kaons
Preliminary
Estimate of net protons at midrapidity
* Assuming 14% more pbar (cf. dN/dη, BRAHMS sub to PRL dec.2001) and 0.75.
NNs 200 GeV (30) (23) (7)*
)(/)( pNpN
* NA49 QM99 & Phys. Rev. Lett. 82, 2471 (1999)
NNs 17 GeV 31 5 26*
* PHENIX nucl-ex/0112006
NNs 130 GeV 29 20 9*
)()(
)(
)(
)(
otherpair
pair
pNpN
pN
pN
pN
N(p) )pN( )pN( -N(p)CM Energy
Summary
First Au+Ausnn=130 ,200 GeV
RESULTS: 100+100 • Nch (0-5%) 5000
• dN/d (y=0) 632. FWHM 7.5
• N(ch) 30 pr. participant-pair
• dN/d (y=0) 3.5/part. pair• p-bar/p higher at y=0,
similar at forward rapidity
RESULTS: 65+65• Nch (0-5%) 4000• dN/d (y=0) 550. FWHM 7.2• N(ch) 23 pr. participant-pair• dN/d (y=0) 3 pr. part. Pair• 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
• Models inconsistent with data