Measurement of $\ensuremath{\phi}$-meson production in $\mathrm{Cu}+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=200$ GeV and $\mathrm{U}+\mathrm{U}$ collisions at $\sqrt{{s}_{NN}}=193$ GeV

Measurement of $ϕ$ -meson production in $Cu + Au$ collisions at $\sqrt{s_{N N}} = 200$ GeV and $U + U$ collisions at $\sqrt{s_{N N}} = 193$ GeV

N. J. Abdulameer et al. (PHENIX Collaboration)

Phys. Rev. C 107, 014907 – Published 13 January 2023

Abstract

The PHENIX experiment reports systematic measurements at the Relativistic Heavy Ion Collider of $ϕ$ -meson production in asymmetric $Cu + Au$ collisions at $\sqrt{s_{N N}} = 200 GeV$ and in $U + U$ collisions at $\sqrt{s_{N N}} = 193 GeV$ . Measurements were performed via the $ϕ \to K^{+} K^{-}$ decay channel at midrapidity $| η | < 0.35$ . Features of $ϕ$ -meson production measured in $Cu + Cu, Cu + Au, Au + Au$ , and $U + U$ collisions were found to not depend on the collision geometry, which was expected because the yields are averaged over the azimuthal angle and follow the expected scaling with nuclear-overlap size. The elliptic flow of the $ϕ$ meson in $Cu + Au, Au + Au$ , and $U + U$ collisions scales with second-order-participant eccentricity and the length scale of the nuclear-overlap region (estimated with the number of participating nucleons). At moderate $p_{T}, ϕ$ -meson production measured in $Cu + Au$ and $U + U$ collisions is consistent with coalescence-model predictions, whereas at high $p_{T}$ the production is in agreement with expectations for in-medium energy loss of parent partons prior to their fragmentation. The elliptic flow for $ϕ$ mesons measured in $Cu + Au$ and $U + U$ collisions is well described by a ( $2 + 1$ )-dimensional viscous-hydrodynamic model with specific-shear viscosity $η / s = 1 / 4 π$ .