kaon production in central au+au collisions at 200 and 63 gev

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Kaon Production in Central Au+Au Collisions at 200 and 63 GeV Djamel Ouerdane Niels Bohr Institute for the BRAHMS Collaboration Strange Quark Matter 2004 Cape Town, September 15-20 BRAHMS

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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 Presentation

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Page 1: Kaon Production in Central Au+Au Collisions at 200 and 63 GeV

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

Page 2: Kaon Production in Central Au+Au Collisions at 200 and 63 GeV

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

Page 3: Kaon Production in Central Au+Au Collisions at 200 and 63 GeV

The BRAHMS Detector

MRS

FFS

BFS

Page 4: Kaon Production in Central Au+Au Collisions at 200 and 63 GeV

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)

Page 5: Kaon Production in Central Au+Au Collisions at 200 and 63 GeV

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

Page 6: Kaon Production in Central Au+Au Collisions at 200 and 63 GeV

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

Page 7: Kaon Production in Central Au+Au Collisions at 200 and 63 GeV

D. Ouerdane, Strange Quark Matter 2004, Cape Town, Sep. 15-20

Kaon Slopes Top 5% central collisions

Page 8: Kaon Production in Central Au+Au Collisions at 200 and 63 GeV

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

Page 9: Kaon Production in Central Au+Au Collisions at 200 and 63 GeV

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

Page 10: Kaon Production in Central Au+Au Collisions at 200 and 63 GeV

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

Page 11: Kaon Production in Central Au+Au Collisions at 200 and 63 GeV

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

Page 12: Kaon Production in Central Au+Au Collisions at 200 and 63 GeV

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 (?)

Page 13: Kaon Production in Central Au+Au Collisions at 200 and 63 GeV

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

Page 14: Kaon Production in Central Au+Au Collisions at 200 and 63 GeV

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