Production of ${K}^{+}$ and of ${K}^{\ensuremath{-}}$ mesons in heavy-ion collisions from 0.6$A$ to 2.0$A$ GeV incident energy

Production of $K^{+}$ and of $K^{-}$ mesons in heavy-ion collisions from 0.6 $A$ to 2.0 $A$ GeV incident energy

A. Förster et al. (KaoS Collaboration)

Phys. Rev. C 75, 024906 – Published 22 February 2007

Abstract

This paper summarizes the yields and the emission patterns of $K^{+}$ and of $K^{-}$ mesons measured in inclusive C+C, Ni+Ni, and Au+Au collisions at incident energies from $0.6 A$ to $2.0 A$ GeV using the Kaon Spectrometer KaoS at GSI. For Ni+Ni collisions at $1.5 A$ and at $1.93 A$ GeV as well as for Au+Au at $1.5 A$ GeV, detailed results are presented of the multiplicities, of the inverse slope parameters, and of the anisotropies in the angular emission patterns as a function of the collision centrality. When comparing transport-model calculations to the measured $K^{+}$ production yields, an agreement is only obtained for a soft nuclear equation of state (compression modulus $K_{N} \approx 200$ MeV). The production of $K^{-}$ mesons at energies around $1 A$ to $2 A$ GeV is dominated by the strangeness-exchange reaction $K^{-} N ⇌ π Y$ ( $Y = Λ, Σ$ ) which leads to a coupling between the $K^{-}$ and $K^{+}$ yields. However, both particle species show distinct differences in their emission patterns suggesting different freeze-out conditions for $K^{+}$ and $K^{-}$ mesons.