Identified charged-hadron production in p+Al , He3+Au , and <mml:mi…

The PHENIX experiment has performed a systematic study of identified charged-hadron (π^±, K^±, $p,$ p̄) production at midrapidity in p+Al, ³He+Au, and Cu+Au collisions at √s_NN=2000.16em0exGeV and U+U collisions at √s_NN=1930.16em0exGeV. Identified charged-hadron invariant transverse-momentum (pT) and transverse-mass (mT) spectra are presented and interpreted in terms of radially expanding thermalized systems. The particle ratios of K/π and p/π have been measured in different centrality ranges of large (Cu+Au and U+U) and small (p+Al and ³He+Au) collision systems. The values of K/π ratios measured in all considered collision systems were found to be consistent with those measured in $p+p$ collisions. However, the values of p/π ratios measured in large collision systems reach the values of ≈0.6, which is a factor of ≈2 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 (RAB) are also presented. Enhancement of proton RAB values over meson RAB values was observed in central ³He+Au, Cu+Au, and U+U collisions. The proton RAB values measured in the p+Al collision system were found to be consistent with RAB values of φ, π^±, K^±, and π⁰ 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.