engleski

Systematic Measurements of Identified Particle Spectra in pp, d+Au and Au+Au Collisions at the STAR detector

We present results for the measurement of $\phi$ meson production via its charged kaon decay channel $\phi \to K^+K^-$ in Au+Au collisions at $\sqrt{; ; ; s_{; ; ; _{; ; ; NN}; ; ; }; ; ; }; ; ; =62.4$, 130, 200 GeV, and in p+p and d+Au collisions at $\sqrt{; ; ; s_{; ; ; _{; ; ; NN}; ; ; }; ; ; }; ; ; =200$ GeV from the STAR experiment at RHIC. The mid-rapidity ($|y|<0.5$) $\phi$ meson spectra in central Au+Au collisions are found to be well described by a single exponential distribution. On the other hand, the spectra from p+p, d+Au and peripheral Au+Au collisions show power-law tails at intermediate and high transverse momenta ($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 $p_{; ; ; T}; ; ; \sim 4$ 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 jet quenching in central Au+Au collisions. Number of constituent quark scaling of both $R_{; ; ; cp}; ; ; $ and $v_{; ; ; 2}; ; ; $ for the $\phi$ meson with respect to other hadrons in Au+Au collisions at $\sqrt{; ; ; s_{; ; ; _{; ; ; NN}; ; ; }; ; ; }; ; ; $=200 GeV at intermediate $p_{; ; ; T}; ; ; $ is observed. These observations support quark coalescence as being the dominant mechanism of hadronization in the intermediate $p_{; ; ; T}; ; ; $ region at RHIC.

meson production via its charged kaon decay

Art. no. 034909