Measurement of ${K}_{S}^{0}$ and ${K}^{*0}$ in $p+p,\phantom{\rule{0.16em}{0ex}}d+\mathrm{Au}$, and Cu + Cu collisions at $\sqrt{{s}_{\mathit{NN}}}=200$ GeV

Measurement of $K_{S}^{0}$ and $K^{* 0}$ in $p + p, d + Au$ , and Cu + Cu collisions at $\sqrt{s_{NN}} = 200$ GeV

A. Adare et al. (PHENIX Collaboration)

Phys. Rev. C 90, 054905 – Published 7 November 2014

Abstract

The PHENIX experiment at the Relativistic Heavy Ion Collider has performed a systematic study of $K_{S}^{0}$ and $K^{* 0}$ meson production at midrapidity in $p + p, d + Au$ , and $Cu + Cu$ collisions at $\sqrt{s_{_{NN}}} = 200$ GeV. The $K_{S}^{0}$ and $K^{* 0}$ mesons are reconstructed via their $K_{S}^{0} \to π^{0} (\to γ γ) π^{0} (\to γ γ)$ and $K^{* 0} \to K^{\pm} π^{\mp}$ decay modes, respectively. The measured transverse-momentum spectra are used to determine the nuclear modification factor of $K_{S}^{0}$ and $K^{* 0}$ mesons in $d + Au$ and $Cu + Cu$ collisions at different centralities. In the $d + Au$ collisions, the nuclear modification factor of $K_{S}^{0}$ and $K^{* 0}$ mesons is almost constant as a function of transverse momentum and is consistent with unity, showing that cold-nuclear-matter effects do not play a significant role in the measured kinematic range. In $Cu + Cu$ collisions, within the uncertainties no nuclear modification is registered in peripheral collisions. In central collisions, both mesons show suppression relative to the expectations from the $p + p$ yield scaled by the number of binary nucleon-nucleon collisions in the $Cu + Cu$ system. In the $p_{T}$ range $2 - 5 GeV / c$ , the strange mesons $(K_{S}^{0}, K^{* 0})$ similarly to the $ϕ$ meson with hidden strangeness, show an intermediate suppression between the more suppressed light quark mesons $(π^{0})$ and the nonsuppressed baryons $(p, \bar{p})$ . At higher transverse momentum, $p_{T} > 5 GeV / c$ , production of all particles is similarly suppressed by a factor of $\approx 2$ .