Measurement of phi-meson production in Cu plus Au collisions at root sNN=200 GeV and U plus U collisions at root sNN=193 GeV

Abstract

The PHENIX experiment reports systematic measurements at the Relativistic Heavy Ion Collider of phi-meson production in asymmetric Cu + Au collisions at root sNN = 200 GeV and in U + U collisions at root sNN = 193 GeV. Measurements were performed via the phi -> K+K- decay channel at midrapidity |n| < 0.35. Features of phi -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 0 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 pT, phi-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 0 mesons measured in Cu + Au and U + U collisions is well described by a (2+1)-dimensional viscous-hydrodynamic model with specific-shear viscosity eta/s = 1/4 pi.