Title

Measurements of Phi Meson Production in Relativistic Heavy-Ion Collisions at the BNL Relativistic Heavy ION Collider (RHIC)

Document Type

Article

Publication Date

6-2009

Abstract

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