engleski

Measurements of φ meson production in relativistic heavy-ion collisions at RHIC

We present results for the measurement of ϕ meson production via its charged kaon decay channel ϕ→K+K− in Au+Au collisions at sNN‾‾‾‾√=62.4, 130, and 200 GeV, and in p+p and d+Au collisions at sNN‾‾‾‾√=200 GeV from the STAR experiment at the BNL Relativistic Heavy Ion Collider (RHIC). The midrapidity (∣∣y∣∣<0.5) ϕ meson transverse momentum (pT) spectra in central Au+Au collisions are found to be well described by a single exponential distribution. On the other hand, the pT spectra from p+p, d+Au, and peripheral Au+Au collisions show power-law tails at intermediate and high pT and are described better by Levy distributions. The constant ϕ/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 ϕ production at RHIC. The Ω/ϕ yield ratio as a function of pT is consistent with a model based on the recombination of thermal s quarks up to pT~4 GeV/c, but disagrees at higher transverse momenta. The measured nuclear modification factor, RdAu, for the ϕ meson increases above unity at intermediate pT, similar to that for pions and protons, while RAA is suppressed due to the energy loss effect in central Au+Au collisions. Number of constituent quark scaling of both Rcp and v2 for the ϕ meson with respect to other hadrons in Au+Au collisions at sNN‾‾‾‾√=200 GeV at intermediate pT is observed. These observations support quark coalescence as being the dominant mechanism of hadronization in the intermediate pT region at RHIC.

phi; meson; STAR

STAR Collaboration.