Identified charged-hadron production in $p$$+$Al, ${}^3$He$+$Au, and Cu$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV and in U$+$U collisions at $\sqrt{s_{{}_{NN}}}=193$ GeV

Abstract

The PHENIX experiment has performed a systematic study of identified charged-hadron (${\pi }^{\pm }$, $K^{\pm }$, $p$, $\bar{p}$) production at midrapidity in $p$$+$Al, ${}^3$He$+$Au, Cu$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV and U$+$U collisions at $\sqrt{s_{{}_{NN}}}=193$ GeV. Identified charged-hadron invariant transverse-momentum ($p_T$) and transverse-mass ($m_T$) spectra are presented and interpreted in terms of radially expanding thermalized systems. The particle ratios of $K/\pi$ and $p/\pi$ have been measured in different centrality ranges of large (Cu$+$Au, U$+$U) and small ($p$$+$Al, ${}^3$He$+$Au) collision systems. The values of $K/\pi$ ratios measured in all considered collision systems were found to be consistent with those measured in $p$$+$$p$ collisions. However the values of $p/\pi$ ratios measured in large collision systems reach the values of $\approx 0.6$, which is $\approx 2$ times larger than in $p$$+$$p$ collisions. These results can be qualitatively understood in terms of the baryon enhancement expected from hadronization by recombination. Identified charged-hadron nuclear-modification factors ($R_{AB}$) are also presented. Enhancement of proton $R_{AB}$ values over meson $R_{AB}$ values was observed in central ${}^3$He$+$Au, Cu$+$Au, and U$+$U collisions. The proton $R_{AB}$ values measured in $p$$+$Al collision system were found to be consistent with $R_{AB}$ values of $\varphi$, ${\pi }^{\pm }$, $K^{\pm }$, and ${\pi }^0$ mesons, which may indicate that the size of the system produced in $p$$+$Al collisions is too small for recombination to cause a noticeable increase in proton production.

arXiv comment480 authors from 78 institutions, 18 pages, 6 tables, 16 figures. v2 is version accepted for publication in Physical Review C. HEPdata tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.html

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