Determination of temperature and transverse flow velocity at chemical freeze-out in relativistic nuclear interactions.

Abstract

We propose a parameter-free method to determine the temperature of a thermalized state in relativistic nuclear interactions, using the experimental ${\mathrm{\ensuremath{\mu}}}_{\mathit{q}}$/T and ${\mathrm{\ensuremath{\mu}}}_{\mathit{s}}$/T values, obtained from strange particle ratios. The hadron gas formalism and strangeness neutrality are employed to relate the quark-chemical potential ${\mathrm{\ensuremath{\mu}}}_{\mathit{q}}$ and ${\mathrm{\ensuremath{\mu}}}_{\mathit{s}}$ to the temperature and thus determine its value at chemical freeze-out. This temperature, together with the inverse slope parameter from ${\mathit{m}}_{\mathit{T}}$ distributions, enable the determination of the transverse flow velocity of the fireball matter, thus disentangling the thermal and flow effects. We study several nucleus-nucleus interactions from AGS and SPS and obtain the temperature, transverse flow velocity, and quark-chemical potentials. Extrapolating the systematics we predict the values of these quantities for ongoing and future experiments at AGS, SPS, and RHIC. We discuss the possibility of reaching the conditions for quark deconfinement and QGP formation and give distinct and identifiable signature. \textcopyright{} 1996 The American Physical Society.