recent results from brahms from y=0 to y=3 i. g. bearden niels bohr institute university of...
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Recent Results from BRAHMS
from y=0 to y=3I. G. BeardenNiels Bohr Institute
University of Copenhagen, Denmark
Quark Matter 2002, July 18-24, Nantes, France
for the
BRAHMS COLLABORATION
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
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. Jacobsen7, A. Jipa10, J. I. Jordre10, F. Jundt2, C.E.Jørgensen7,
R. Karabowicz4 , 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. Mikkelsen12, M. Murray8, J. Natowitz8, B.S.Nielsen7, K. Olchanski1, 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, France
3Jagiellonian University, Cracow, Poland, 4Institute of Nuclear Physics, Cracow, Poland5Johns Hopkins University, Baltimore, USA, 6New York University, USA
7Niels Bohr Institute, Blegdamsvej 17, University of Copenhagen, Denmark8Texas A&M University, College Station. USA, 9University of Bergen, Norway 10University of Bucharest, Romania, 11University of Kansas, Lawrence,USA
12 University of Oslo Norway
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
The BRAHMS Experiment
95°
30°
30°
15°
2.3°
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Determination of Collision Vertex, Centrality
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Sys. Error :
10%
8%
0-5%
5-10%
10-20
Multiplicity density @ 200GeV
100AGeV+100 AGeV:
N(ch)d= 4630 • Central 0-5% dN(ch)/d (=0)
=632• FWHM of
distribution = 7.5 0.5
For details, see the BRAHMS poster by S. Sanders, H. Ito.
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Limiting fragmentation
Shift data to beam frame of reference
PRL 88 (2002) 2002301 BRAHMS
PLB 523 (2001) 227 BRAHMS
Phys Rev C (2000)62 014903
Moving awayfrom
midrapidity particle productio
nlooks like
SPS
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
dNch/d: Comparison to Models
SNN=200GeV
AMPT
High density QCDgluon saturationKharzeev and Levin,PLB523(2001)79
Differences forPeripheral Collisions but Small effect !
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMSMRS
FORWARD
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
PID in BRAHMS
MRSTOF
FSTOF
FSTOF+C1
RICH
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Ratios are (relatively) easy...
Ratios could vary in pt, and in yNarrow y bins, look vs pt
geometric acceptance same for
particles and antiparticles, so
correction is not needed.For given B field, angular setting, compare (+) and (-) polarity
Normalize to number of triggers, and --bingo!-- ratios....
No dependence on transverse momentum or centralitySee poster for details of the analysis!
4o
8o
12o
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Particle/Particle vs rapidity
BRAHMS, submitted to PRL12/07/02 nucl-ex/0207006
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
BRAHMS, submitted to PRL12/07/02 nucl-ex/0207006
Becattini: T=170, s=1
PBM (PhysLettB518
(2000)41) predicts y=0
ratios almost exactly
K-/K+=
exp(2s/T)(pbar/p)1/3
K- /K+=(pbar/p)1/4 is
a fit to the data points
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Top 10% central
K+ p cross~1.2GeV/
cP pion cross
>2GeV/c?
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Not surprisingly, the antiparticle spectra don’t look much different...at y=0!
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
,p cross1.2 GeV/c
p>K overcovered pT
Only small part of high rapidity data analyzed...so far.
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Pbar , K- yield lowerthan p, K+
Pbar,- cross at higher pT
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Inverse pT Slope
vs. mass...
Nb: all fits are in pt, oversame range for all particles,
at all rapidities
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Strangeness : ratio K/
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
y = 3 similar to SPS
Strangeness : K/ systematics
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
p and pbar yields0-10%: BRAHMS Preliminary SNN=200 GeV: 0-10% Central
y = 0
y=0.8
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
p and pbar at y=2.9BRAHMS Preliminary
antiprotonYield =10.5 0.8 1.6 (Inverse pt slope =325.517.3)
proton Yield = 33.7 1.8 5.1
(Inverse pt slope = 341.8 13.8
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Net protons, first shot...
BRAHMS Preliminary
d2N/dpTdy
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Net protons vs Rapidity!
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Can we kill models?
Points scaled by 2
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Q’AMPT
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
High pt
y=0
y=0 High pt
y=2.2
C.E.Jørgensen Parallel session I today.
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Future plans...• Analyze complete data set at high
rapidity – Better pt coverage– (slightly) higher y
• Spectra, yields for 1<y<3• Source size at mid, forward rapidity• p+p data • Longer term...
– Upgrades better high pt PID in MRS
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Summary• K-/K+, pbar/p ratios fall off with rapidity• Universal correlation between K-/K+ and pbar/p• K-/- decreases from 0.15 (y=0) to 0.1(y=3)• Inverse slope decreases with rapidity• Measured dN/dy over 3 units of rapidity.• Dramatic increase in net protons at y=3Low to high chemical potential from y=0 to
y=3Net baryon central plateau (y=0 to almost y=2)Significant transparency
I.G.Bearden, Niels Bohr Institute 20 July 2002
BRAHMS
Radius versus Momentum
Zoom in
RICH used for PIDp>15GeV/cK>8 GeV/c>4 GeV/c