$\ensuremath{\phi}$ meson production in $p+\mathrm{Al},$ $p+\mathrm{Au},$ $d+\mathrm{Au},$ and $^{3}\mathrm{He}+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=200\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}$

$ϕ$ meson production in $p + Al,$ $p + Au,$ $d + Au,$ and ${}^{3}{He} + Au$ collisions at $\sqrt{s_{N N}} = 200 GeV$

U. Acharya et al. (PHENIX Collaboration)

Phys. Rev. C 106, 014908 – Published 26 July 2022

Abstract

Small nuclear collisions are mainly sensitive to cold-nuclear-matter effects; however, the collective behavior observed in these collisions shows a hint of hot-nuclear-matter effects. The identified-particle spectra, especially the $ϕ$ mesons which contain strange and antistrange quarks and have a relatively small hadronic-interaction cross section, are a good tool to study these effects. The PHENIX experiment has measured $ϕ$ mesons in a specific set of small collision systems $p + Al$ , $p + Au$ , and ${}^{3}{He} + Au$ , as well as $d + Au$ [Adare et al., Phys. Rev. C 83, 024909 (2011)], at $\sqrt{s_{_{N N}}} = 200$ GeV. The transverse-momentum spectra and nuclear-modification factors are presented and compared to theoretical-model predictions. The comparisons with different calculations suggest that quark-gluon plasma may be formed in these small collision systems at $\sqrt{s_{_{N N}}} = 200$ GeV. However, the volume and the lifetime of the produced medium may be insufficient for observing strangeness-enhancement and jet-quenching effects. The comparison with calculations suggests that the main production mechanisms of $ϕ$ mesons at midrapidity may be different in $p + Al$ versus $p / d / {}^{3}{He} + Au$ collisions at $\sqrt{s_{_{N N}}} = 200$ GeV. While thermal quark recombination seems to dominate in $p / d / {}^{3}{He} + Au$ collisions, fragmentation seems to be the main production mechanism in $p + Al$ collisions.