A. Wojtaszek

System-size dependence of Λ and Ξ production in nucleus-nucleus collisions at 40A and 158A GeV measured at the CERN Super Proton Synchrotron

T. Anticic, B. Baatar, D. Barna, J. Bartke, H. Beck, L. Betev, H. Bia lkowska, C. Blume, B. Boimska, J. Book, M. Botje, J. Bracinik, P. Bunčić, V. Cerny, P. Christakoglou, P. Chung, O. Chvala, J.G. Cramer, P. Csató, P. Dinkelaker, V. Eckardt, Z. Fodor, P. Foka, V. Friese, J. Gál, M. Gaździcki, 11 V. Genchev, K. Grebieszkow, S. Hegyi, C. Höhne, K. Kadija, A. Karev, D. Kresan, V.I. Kolesnikov, M. Kowalski, I. Kraus, M. Kreps, A. Laszlo, R. Lacey, M. van Leeuwen, P. Lévai, L. Litov, B. Lungwitz, M. Makariev, A.I. Malakhov, M. Mateev, G.L. Melkumov, C. Meurer, A. Mischke, M. Mitrovski, J. Molnár, St. Mrówczyński, V. Nicolic, G. Pálla, A.D. Panagiotou, D. Panayotov, A. Petridis, ∗ W. Peryt, M. Pikna, J. Pluta, D. Prindle, F. Pühlhofer, R. Renfordt, C. Roland, G. Roland, M. Rybczyński, A. Rybicki, A. Sandoval, N. Schmitz, T. Schuster, P. Seyboth, F. Siklér, B. Sitar, E. Skrzypczak, M. Slodkowski, G. Stefanek, R. Stock, C. Strabel, H. Ströbele, T. Susa, I. Szentpétery, J. Sziklai, M. Szuba, P. Szymanski, M. Utvić, D. Varga, 10 M. Vassiliou, G.I. Veres, 5 G. Vesztergombi, D. Vranić, Z. W lodarczyk, A. Wojtaszek, and I.K. Yoo

A new SPS programme

A new experiemntal program to study hadron production in hadron-nucleus and nucleus-nucleus collisions at the CERN SPS has been recently proposed by the NA49-future collaboration. The physics goals of the program are: -Search for the critical point of strongly interacting matter and a study of the properties of the onset of deconfinemnt in nucleus-nucleus collisions, -Measurements of correlations, fluctuations and hadron spectra at high pT in proton-nucleus collisions needed as for better understanding of nucleus-nucleus results, -Measurements of hadron production in hadron-nucleus interactions needed for neutrino (T2K) and cosmic-ray (Pierre Auger Observatory and KASCADE) expriments. The physics of the nucleus-nucleus program is reviewed in this presentation.

Three-dimensional two-pion source image from Pb+Pb collisions at √ sNN=17.3 GeV: new constraints for source breakup dynamics

Abstract Source imaging methodology is used to provide a three-dimensional two-pion source function for mid-rapidity pion pairs with p T 70 MeV / c in central (0–7%) Pb + Pb collisions at s NN = 17.3 GeV . Prominent non-Gaussian tails are observed in the pion pair transverse momentum (outward) and in the beam (longitudinal) directions. Model calculations reproduce them with the assumption of Bjorken longitudinal boost invariance and transverse flow blast-wave dynamics; they also yield a proper time for breakup and emission duration for the pion source.

Elliptic flow of Λ hyperons in Pb+Pb collisions at 158A GeV

The elliptic flow of Lambda hyperons has been measured by the NA49 collaboration at the CERN-SPS in semi-central Pb+Pb collisions at 158A GeV. The standard method of correlating particles with the event plane was used. Measurements of v2 near mid-rapidity are reported as a function of rapidity, centrality and transverse momentum. Elliptic flow of Lambda particles increases both with the impact parameter and with the transverse momentum. It is compared with v2 for pions and protons as well as with model calculations. The observation of significant elliptic flow and its mass dependence suggest strong collective behaviour of the matter produced in collisions of heavy nuclei already at the SPS. Scaling properties of elliptic flow of different particle species have been tested at 158A GeV. The limited pT range of the data does not allow for a decisive test of the coalescence model.