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HK: Hadronen und Kerne

HK 24: Heavy Ion Reactions III, Ultrarelativistic Energies

HK 24.2: Vortrag

Dienstag, 17. März 1998, 14:15–14:30, P

Production of Neutral Mesons in Pb-induced Reactions at 158 A GeV ^* — •C. Blume¹, C. Barlag¹, S. Bathe¹, Z. B"or"ocz¹, D. Bucher¹, H. B"usching¹, S. Gorus¹, R. Glasow¹, S. Joerrens¹, H. K"ohncke¹, T. Kr"umpel¹, T. Peitzmann¹, K. Reygers¹, R. Santo¹, H. Schlagheck¹, and WA98² — ¹Institut f"ur Kernphysik, Universit"at M"unster, D-48149 M"unster — ²

The measurement of distributions of produced neutral mesons offers the possibility to study the condition of the fireball which is produced in ultra-relativistic heavy ion collisions at freeze-out. Especially the question whether a thermal or chemical equilibrium is achieved during the lifetime of the excited nuclear matter is of high interest.

We present a systematic study of π⁰ p_T-spectra of the reaction of Pb-Ions with Pb-, Nb-, and Ni-target at 158 A GeV as measured with the LEDA-spectrometer of the WA98 experiment. We will discuss the dependence of the π⁰-yield and ⟨ p_T ⟩ on the number of participants. The spectra will also be compared to various hydrodynamical models. These calculations include radial flow and allow to set constraints on the flow velocity. The question of whether a chemical equilibrium exists in these reactions can be studied by the measurement of ratios of the yields of different particle species. We present our result on the yield of η-mesons and compare this to results from other experiments and to predictions from m_T-scaling.

^* Partly supported by the German BMBF and the GSI.