Study of $\ddot{I}•$-meson production in $p$$+$Al, $p$$+$Au, $d$$+$Au, and ${}^3$He$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV

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 $\ddot{I}•$ 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 $\ddot{I}•$ mesons in a specific set of small collision systems $p$$+$Al, $p$$+$Au, and ${}^3$He$+$Au, as well as $d$$+$Au [Phys. Rev. C {\bf 83}, 024909 (2011)], at $\sqrt{s_{{}_{NN}}}=200$ GeV. The transverse-momentum spectra and nuclear-modification factors are presented and compared to theoretical-model predictions. The comparisons with different calculations suggest that quark-gluon plasma may be formed in these small collision systems at $\sqrt{s_{{}_{NN}}}=200$ GeV. However, the volume and the lifetime of the produced medium may be insufficient for observing strangeness-enhancement and jet-quenching effects. Comparison with calculations suggests that the main production mechanisms of $\ddot{I}•$ mesons at midrapidity may be different in $p$$+$Al versus $p/d/$${}^3$He$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV. While thermal quark recombination seems to dominate in $p/d/$${}^3$He$+$Au collisions, fragmentation seems to be the main production mechanism in $p$$+$Al collisions.

371 authors from 72 institutions, 13 pages, 7 figures, 7 tables, 2014 and 2015 data. v2 is version accepted for publication Physical Review C. Plain text data 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