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

The PHENIX experiment has performed a systematic study of identified charged-hadron ($π^±$, $K^±$, $p$, $\overline{p}$) production at midrapidity in $p$ + Al, 3He +Au, and 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 $K/π$ 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 ($R_{AB}$) are also presented. Enhancement of proton $R_{AB}$ values over meson $R_{AB}$ values was observed in central 3He +Au, Cu + Au, and U + U collisions. Here, the proton $R_{AB}$ values measured in the $p$ + Al collision system were found to be consistent with $R_{AB}$ values of $Φ$, $π^±$, $K^±$, and $π^0$ 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.