Towards MatterAntimatter Balance at RHIC

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BRAHMS results from AuAu at GeV
BRAHMS
Presented by Peter Christiansen, NBI At the 18th
Winter Workshop on Nuclear Dynamics
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The BRAHMS Collaboration
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, 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,
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 AM University, College Station.
USA, 9University of Bergen, Norway 10University
of Bucharest, Romania, 11University of Kansas,
Lawrence,USA 12 University of Oslo Norway
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The BRAHMS Experiment
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Global detectors
BB Provide vertex and start time for TOF (and
forward multiplicity)
MA Provide multiplicity / centrality of
collision
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BRAHMS Preliminary
0-5
4630 370 charged particles produced for 0-5
central. 21 increase over 130 GeV dNch/d?
(?0) 625 55(syst.) 14 increase over 130
GeV. Phobos 200 GeV PRL 88, 22302 dNch/d?
(?0) 650 35(syst.) 200 GeV Submitted to
PRL (nucl-ex/0112001) 130 GeV Phys. Lett. B
523, p. 227
5-10
10-20
20-30
30-40
40-50
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Comparison to scaled and models
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The BRAHMS Experiment
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Vertex
Beam Line
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Time-of-flight Wall TOFW
125 scintillator slats TOF resolution s ? 100
ps p/K separation up to ? 2 GeV/c
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PID in the front-forward spectrometer
D2
C1
T2
H1
TOF wall H1 (40 slats TOF resolution s ? 65 ps)
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Ring Imaging Cherenkov
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BRAHMS Acceptance
PID over a broad range of rapidity and
transverse momentum.

• PID in MRS via TOFW

• PID in FS via
• TOF1, C1, TOF2 and RICH

Transverse momentum GeV/c
Rapidity
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Ratios of particles and anti-particles at
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.
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Ratios vs Pt and centrality
BRAHMS Preliminary
BRAHMS Preliminary
No sign of Pt or centrality dependence
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Rapidity dependence of ratios at .
BRAHMS Preliminary
(and feeddown)
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Energy Systematics (y0)
BRAHMS Preliminary
BRAHMS Preliminary
ISR R803
- towards matter-antimatter balance.
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Towards spectra
Data MRS at 90 degrees 2 fields 2.1 kG /
-2.1 kG 6 vtx bins 15.0 to 15.0 (200k / 170k)
25 events
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(No Transcript)
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Simulating the acceptance
GEANT package. Correct Geometry and
instrumentation. Decays and scattering of
particles on beam pipe and detector material is
included. The acceptance is here the propability
that a single thrown particle will hit enough
detector elements to be identified.
2.5º
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Acceptance corrected Pt spectra
Does not take into account Detector/Tracking
inefficiencies Secondaries
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Spectra results (y0)
BRAHMS Preliminary
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BRAHMS Preliminary
BRAHMS Preliminary
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Conclusion and outlook
Charged multiplicity (0-5) 4630, 20 increase
from 130 GeV. dNch/d? (?0) 625, 14 increase
from 130 GeV, 50 increase from scaled
ppbar. Weak rapidity dependence on k
ratio. Strong rapidity dependence of p ratio at a
level higher than at 130 GeV indicates more
transparent collisions. This seems also to be
supported by the net baryon yield which is lower
than at 130 (STAR). K/p and pbar /p comparable
to 130 GeV (PHENIX). Include more details in the
detector simulation. Combine angular settings and
fields to get yields at more rapidities. Use the
forward spectrometer to get yields at forward
rapidities.