kaon production in central au+au collisions at 200 and 63 gev
DESCRIPTION
Kaon Production in Central Au+Au Collisions at 200 and 63 GeV. BRAHMS. Djamel Ouerdane Niels Bohr Institute for the BRAHMS Collaboration. Strange Quark Matter 2004 Cape Town, September 15-20. Outline of the Talk. The BRAHMS experiment p T Spectra : slope systematic - PowerPoint PPT PresentationTRANSCRIPT
Kaon Production in Central Au+Au Collisions at 200 and 63 GeV
Djamel OuerdaneNiels Bohr Institute
for the BRAHMS Collaboration
Strange Quark Matter 2004Cape Town, September 15-20
BRAHMS
D. Ouerdane, Strange Quark Matter 2004, Cape Town, Sep. 15-20
Outline of the Talk
• The BRAHMS experiment
• pT Spectra : slope systematic
• Rapidity distributions : K vs
• Kaon and B
• Conclusion
The BRAHMS Detector
MRS
FFS
BFS
D. Ouerdane, Strange Quark Matter 2004, Cape Town, Sep. 15-20
Particle Identification
1
L
TOFcpm
2
2222TIME-OF-FLIGHT
Particle Separation: pmax (2 cut)=
TOFW TOF1 TOF2
/ K
2 cut
K / p
2 GeV/c 3 GeV/c 4.5 GeV/c
3.5GeV/c 5.5GeV/c 7.5GeV/c
RICH: Cherenkov light focusedon spherical mirror ring on image plane
Ring radius vs momentum gives PID / K separation 20 GeV/cProton ID up to 35 GeV/c
CHERENKOV
(2 settings)
D. Ouerdane, Strange Quark Matter 2004, Cape Town, Sep. 15-20
Kaon @ 200 GeV invariant differential yields
Kaon @ 62.4 GeV invariant differential yields
By combining all data sets and averaging over the number of collisions,we get the final invariant yields over a broad range of phase-space
Kaon Spectra
Spectra : projection of rapidity intervals to pT axis
D. Ouerdane, Strange Quark Matter 2004, Cape Town, Sep. 15-20
Kaon Spectra
Fit: exponential
T
mmA Texp
Top 5% central collisions
AuAu 63 GeV
AuAu 200 GeV
D. Ouerdane, Strange Quark Matter 2004, Cape Town, Sep. 15-20
Kaon Slopes Top 5% central collisions
D. Ouerdane, Strange Quark Matter 2004, Cape Town, Sep. 15-20
Integrated multiplicities @ 200 GeV (Gaussian fit)
N(K+) ~ 290 N(K) ~ 240
Rapidity Densities
D. Ouerdane, Strange Quark Matter 2004, Cape Town, Sep. 15-20
Rapidity Densities
Width after Gaussian fit:AGS ~ no dependence
SPS-RHIC ~ strongdependence : longitudinalflow important
D. Ouerdane, Strange Quark Matter 2004, Cape Town, Sep. 15-20
Y < 1 : consistent with Hadron Gas Stat. ModelK+/+ : 15.6 0.1 % (stat)K/ : 14.7 0.1 % (stat) [Phys. Lett. B 518 (2001) 41]
Divergence at higher y :Associated K+ productionNo single source with
unique T and B
Kaons vs PionsRAPIDITY DEPENDENCE
D. Ouerdane, Strange Quark Matter 2004, Cape Town, Sep. 15-20
At y = 0, ratios convergeto ~ 15 %
ENERGY DEPENDENCE
Why max AGS-SPS ?Net-Kaon distributionevolves like net-proton
Over the full phase space:K+/+ = 16.6 1.5 % (syst)K/ = 13.7 2.0 % (syst)
Kaons vs Pions
D. Ouerdane, Strange Quark Matter 2004, Cape Town, Sep. 15-20
ENERGY DEPENDENCE
Kaons vs B
BRAHMS, PRL90 (2003) 102301
T~constant, B varies with y
Net-kaon and net-protondistributions at 3 different beamenergies
T~ constant, B drives ratiosin y or beam energy (?)
D. Ouerdane, Strange Quark Matter 2004, Cape Town, Sep. 15-20
Summary & ConclusionsTransverse momentum spectra of kaons measured in rapidity range
-0.1 < yK < 3.4 for central Au+Au collisions at 200 and 63 GeV
SLOPES: exponential in mT gives good description slopes at 200 GeV > 63 GeV, small step
YIELDS: N(+) ~ N(-) at mid-rapidity (47 and 44) but N(+) > N(-) at y > 2 due to associated K+ production
K / converge to ~ 15% at y ~ 0 (plateau y < 1) same within systematic errors for full phase-space ratios possible indication of strangeness equilibration at 200 GeV At 63 GeV, y = 0, ratios at “expected” values
K vs B B seems to drive the kaon ratio in rapidity and energy with T~ constant, preliminary 63 GeV data consistent with this
D. Ouerdane, Strange Quark Matter 2004, Cape Town, Sep. 15-20
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. 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, France3Jagiellonian University, Cracow, Poland, 4Institute of Nuclear Physics, Cracow, Poland
5Johns Hopkins University, Baltimore, USA, 6New York University, USA7Niels Bohr Institute, 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