Azimuthal emission patterns of ${K}^{+}$ and of ${K}^{\ensuremath{-}}$ mesons in Ni + Ni collisions near the strangeness production threshold

Azimuthal emission patterns of $K^{+}$ and of $K^{-}$ mesons in Ni + Ni collisions near the strangeness production threshold

V. Zinyuk et al. (FOPI Collaboration)

Phys. Rev. C 90, 025210 – Published 25 August 2014

Abstract

Azimuthal emission patterns of $K^{\pm}$ mesons have been measured in Ni + Ni collisions with the FOPI spectrometer at a beam kinetic energy of 1.91 A GeV. The transverse momentum $p_{T}$ integrated directed and elliptic flow of $K^{+}$ and $K^{-}$ mesons as well as the centrality dependence of $p_{T}$ - differential directed flow of $K^{+}$ mesons are compared to the predictions of hadron string dynamics and isospin quantum molecular dynamics transport models. The data exhibits different propagation patterns of $K^{+}$ and $K^{-}$ mesons in the compressed and heated nuclear medium and favor the existence of a kaon-nucleon in-medium potential, repulsive for $K^{+}$ mesons and attractive for $K^{-}$ mesons.