strangeness production in heavy ion collisions at sps energies

HEP2003 - July 19, 2003Andre Mischke 1

Strangeness Productionin

Heavy Ion Collisions at SPS Energies

André Mischke

for the NA49 Collaboration

a.mischke@phys.uu.nl

HEP2003 - July 19, 2003Andre Mischke 2

Outline

• Physics Programme

• Experimental Setup

• Particle Identification / V0-Reconstruction

• Spectra on Kaons, and

• Energy Dependence

• Baryon Ratios

• Summary

HEP2003 - July 19, 2003Andre Mischke 3

Physics Programme in NA49

• Search for the onset of deconfinement

• Energy scan programme at CERN-SPS (started in ‘99)

- central Pb-Pb events at 20, 30, 40, 80 and 158 AGeV

• Search for anomalies in the energy dependence of physical observables; here strangeness production

- s quarks are mainly carried by the

- essentially half of thes quarks are contained in K+

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NA49 Detector at CERN-SPS

• Fixed target experiment

• Large acceptance hadron

spectrometer

Event display:~1200 charged particles

• 2 super-conducting dipole magnets, 9 Tm bending power

• 4 volume TPC’s for tracking and PID via dE/dx

• 2 ToF walls for PID at mid-rapidity

• 180,000 channels

• Event rate ~7 Hz

NIM A430, 210 (1999)

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Identification of Charged Particles

Specific energy loss dE/dx:

• cover forward rapidity (p > 7 GeV/c)

• dE/dx resolution ~ 4%

Time-of-Flight:

• at mid-rapidity

• resolution ~ 60ps

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V0 - Reconstruction

Neutral strange particles are identified

by their decay topology:

p + - (64.1 %)

For the spectra: contain 0

Invariant mass spectra

- measured mass in agreement with PDG

- mass resolution 2 MeV/c2

158 AGeV158 AGeV

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Kaons: Transverse Spectra

at mid-rapidity

Slopes are similar for K+ and K-

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Kaons: Rapidity Distributions

published: PRC 66, 054902 (2002)preliminaryshown on SQM2003

K+ broader than K-

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Energy Dependence of K/ ratio

Pronounced maximum Kink-like structure

RHIC

published

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: Transverse Spectra

Slope parameter slightly increases with increasing energy

at mid-rapidity

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: Rapidity Distributions

• broader than• Flattening of the rapidity distribution

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Energy Dependence of / ratio

Non-monotonic energy dependence Continuous rise

)-π+(π 1.5 = π +nucl-ex/0209002

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Strangeness Enhancement in Production

N K dominant process

• Same behaviour for the K+/+ ratio

• Strangeness enhancement not a unique signature for QGP formation

hep-ph/0209284

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Spectra on

Slope increases with energy

(ss) K+K-

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: Energy Dependence40 AGeV 80 AGeV 158 AGeV

NA49 Preliminary

PLB 491, 59 (2000)

/ increases monotonically

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First measurements of rapidity distribution in Pb-Pb at 158 AGeV!(presented on QM2002)

Multi-strange Baryons

40 AGeV 40 AGeV

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Effect of Baryon Density

• Strong increase with energy due to decreasing baryon density

• Particle ratios increase with the number of valence s/sbar quarks in the baryon

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Summary

• Large data sets available for the SPS energy range from 20 to 158 GeV per nucleon

• Excitation function of K and production in HIC:

- Pronounced maximum in the K+/+ ratio around 30 AGeV

- / ratio shows a maximum at the same energy

/ ratio increases monotonically with cms energy

• First results on multi-strange hyperons at lower SPS energies

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Collaboration

T. Anticic, B. Baatar, D. Barna, J. Bartke, M. Behler, L. Betev, H. Bialkowska,

A. Billmeier, C. Blume, B. Boimska, M. Botje, J. Bracinik, F.P. Brady, R. Bramm,

R. Brun, P. Buncic, V. Cerny, P. Christakoglou, J.G. Cramer, P. Csato, P. Dinkelacker,

V. Eckardt, F. Eckhardt, P. Filip, H.G. Fischer, Z. Fodor, P. Foka, P. Freund, V. Friese,

J. Gal, M. Gaździcki, G. Georgopoulos, E. Gladysz, S. Hegyi, C. Höhne, K. Kadija,

A. Karev, V.I. Kolesnikov, T. Kollegger, R. Korus, M. Kowalski, I. Kraus, M. Kreps,

M. van Leeuwen, B. Lasiuk, M. van Leeuwen, P. Levai, A.I. Malakhov, C. Markert,

B.W. Mayes, G.L. Melkumov, C. Meurer, A. Mischke, M. Mitrovski, J. Molnar,

St. Mrowczynski, G. Palla, A.D. Panagiotou, K. Perl, A. Petridis, M. Pikna, L. Pinsky,

F. Pühlhofer, J.G. Reid, R. Renfordt, W. Retyk, C. Roland, G. Roland, M. Rybczynski,

A. Rybicki, A. Sandoval, H. Sann, N. Schmitz, P. Seyboth, F. Sikler, B. Sitar,

E. Skrzypcak, G. Stefanek, R. Stock, H. Ströbele, T. Susa, I. Szentpetery, J. Sziklai,

T.A. Trainor, D. Varga, M. Vassiliou, G.I. Veres, G. Vesztergombi, D. Vranic ,

S. Wenig, A. Wetzler, Z. Wlodarczyk, I.K. Yoo, J. Zaranek, J. Zimanyi

20 Institutes from 12 nations96 participants

HEP2003 - July 19, 2003Andre Mischke 20

Add. Slide(s)

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Energy Dependence of Pion Production