Measurements of phi meson production in relativistic heavy-ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC)

Abstract

We present results for the measurement of ϕ meson production via its charged kaon decay channel ϕ→K[superscript +]K[superscript -] in Au+Au collisions at √(s[subscript NN])=62.4,130, and 200 GeV, and in p+p and d+Au collisions at √(s[subscript NN])=200 from the STAR experiment at the BNL Relativistic Heavy Ion Collider (RHIC). The midrapidity (|y|<0.5) ϕ meson transverse momentum (p[subscript T]) spectra in central Au+Au collisions are found to be well described by a single exponential distribution. On the other hand, the p[subscript T] spectra from p+p, d+Au, and peripheral Au+Au collisions show power-law tails at intermediate and high p[subscript T] and are described better by Levy distributions. The constant ϕ/K[superscript -] yield ratio vs beam species, collision centrality, and colliding energy is in contradiction with expectations from models having kaon coalescence as the dominant mechanism for ϕ production at RHIC. The Ω/ϕ yield ratio as a function of p[subscript T] is consistent with a model based on the recombination of thermal s quarks up to p[subscript T]~4 GeV/c, but disagrees at higher transverse momenta. The measured nuclear modification factor, RdAu, for the ϕ meson increases above unity at intermediate p[subscript T], similar to that for pions and protons, while R[subscript AA] is suppressed due to the energy loss effect in central Au+Au collisions. Number of constituent quark scaling of both R[subscript cp] and v[subscript 2] for the ϕ meson with respect to other hadrons in Au+Au collisions at √(sNN)=200 GeV at intermediate p[subscript T] is observed. These observations support quark coalescence as being the dominant mechanism of hadronization in the intermediate p[subscript T] region at RHIC.