Strangeness production in Au+Au collisions at RHIC

Jens Ivar Jørdre

University of Bergen, Norway

Brief outline

Motivations

Experimental setup

mT spectra

Kinematics: <pT>

Yields and ratios

Dependence on experimental parameters

Comparison to other experiments and models

Au

Au

space

time

Chemical freeze out

Expansion

Mixed

QGP

Thermalization

Pre equilibrium

p

K

Motivation

T. Chujo, PHENIX collaboration, QM02

Probe the chemical bulk properties

Possible probe for the state of nuclear matter phase

The BRAHMS experiment

K and  spectra

BRAHMS PRELIMINARY

Ph.D thesis by D.Ouerdane, NBI

Mean pT

BRAHMS PRELIMINARY

STAR / PHENIX:

saturation of <pT> at y~0 with increasing centrality: 15-20% increase in <pT> for kaons and 20-25% for pions

<pT> estimated from fit functions

Slow decrease in <pT> for kaons and pions

possibly a slightly steeper gradient for kaons

Overall slighty less transverse expansion at y=3 than at y=0

Yields

Single Gaussian

preliminary fits:

Plateau at y ~ 0? No conclusive answer.

s(p+) = 2.28  0.02

s(p-) = 2.33  0.02

s(K+) = 2.42  0.06

s(K-) = 2.12  0.04

BRAHMS PRELIMINARY

Kaon dN/dy vs lower energies

S.V.Afanasiev et al., NA49 collaboration

[Phys. Rev. C 66, 054902 (2002)]

L.Ahle et al., E866/E917 collaboration

[nucl-ex/9910008]

[Phys. Lett. B 490, 53 (2002)]

[Phys. Rev. C 60, 044904 (1999)]

The shape of the K+ distribution still wider than of K-. However they approach each other.

BRAHMS PRELIMINARY

Like particle ratios

I.G.Bearden et al., BRAHMS collaboration

[Phys. Rev. Lett. 90, 102301 (2002)]

Comparison to thermal model

I. G. Bearden et al., BRAHMS collaboration

[Phys. Rev. Lett. 90, 102301 (2002)]

F. Becattini et al.,

[Phys. Rev. C 64, 024901 (2001)]

RHIC, SPS and AGS data well described by thermal model.

K/(y)

BRAHMS PRELIMINARY

K+/p+ constant throughout BRAHMS' acceptance

K- /p- decreases with increasing y

K/( )

J.L.Klay et al. (E895 collaboration)

[nucl-ex/0306033]

L.Ahle et al. (E866/E917 collaboration)

[Phys. Rev. C 60, 044904 (1999)]

[Phys. Lett. B 490, 53 (2000)]

S.V.Afanasiev et al. (NA49 collaboration)

[Phys. Rev. C 66, 054902 (2002)]

I.G.Bearden et al. (NA44 collaboration)

[Phys. Lett. B 471, 6 (1999)]

C.Adler et al. (STAR collaboration)

[nucl-ex/0206008]

O.Barannikova, F.Wang (STARcollaboration)

[Talk at QM02]

K.Adcox et al. (PHENIX collaboration)

[Phys. Rev. Lett. 88, 242301 (2002)]

BRAHMS PRELIMINARY

Comparison to more models

Description of pions not too far off, especially at high rapidity.

Kaon description off by about ¼ at midrapidity.

Thus also K/.

BRAHMS PRELIMINARY

Summary

The BRAHMS experiment shows interesting results on strangeness in a wide rapidity window, |y| < 3.5:

Slow decrease of <pT> with increasing y, possibly stronger decrease for kaons than for pions

dN/dy (y) described well by Gaussian, with comparable s for p and K

K/p ratios vs : K+/p+ saturated while K-/p- still rising

Thermal model describes K+/K- vs pp nicely

The Hijing and AMPT models fail in particular in describing kaons

rapidity distribution

The BRAHMS collaboration

I. Arsene10, I. G. Bearden7, D. Beavis1, C. Besliu10, 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, H. Ito1, 11, A. Jipa10, F. Jundt2, J. I. Jørdre9, C. E. Jørgensen7,

R. Karabowicz3, E. J. Kim5, T. Kozik3, T. M. Larsen12, J. H. Lee1, Y. K. Lee5, S. Lindal12, R. Lystad9,

G. Løvhøiden2, Z. Majka3, A. Makeev8, B. McBreen1, M. Mikelsen12, M. Murray8, 11, J. Natowitz8,

B. Neumann11, B. S. Nielsen7, J. S. Norris11, D. Ouerdane7, R. Planeta4, F. Rami2, C. Ristea10, O. Ristea10,

D. Röhrich9, B. H. Samset12, D. Sandberg7, S. J. Sanders11, R. A. Scheetz1, P. Staszel7, T. S. Tveter12,

F. Videbæk1, R. Wada8, Z. Yin9, I. S. Zgura10

1Brookhaven National Laboratory, USA,

2IReS and Université Louis Pasteur, Strasbourg, France

3Jagiellonian University, Krakow, Poland,

4Institute of Nuclear Physics, Krakow, Poland

5Johns Hopkins University, Baltimore, USA,

6New York University, USA

7Niels 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

Pion dN/dy compared to lower energies

BRAHMS PRELIMINARY

Comparable shape of pions distributions

Jens Ivar Jordre

2003-07-08T18:09:20

Jens Ivar Jordre