Modification of $\hat{I}\yen$ production in $p$O and OO collisions at LHCb

Abstract

The production rates of $\hat{I}\yen (2S)$ and $\hat{I}\yen (3S)$ mesons relative to that of the $\hat{I}\yen (1S)$ state are measured in $pp$, $p$O, and OO collisions by the LHCb collaboration. The ratios measured in $pp$ data are consistent with previous LHCb measurements at different center-of-mass energies. Only slight relative suppression of the $\hat{I}\yen (2S)$ and $\hat{I}\yen (3S)$ states is found in $p$O collisions, while in OO collisions the $\hat{I}\yen (2S)$ is suppressed by a factor of $\sim 2$, with evidence for suppression of the $\hat{I}\yen (3S)$. The significant suppression in OO data, compared to the small effect in $p$O data, shows the emergence of additional suppression mechanisms in the relatively small OO collision system. Models incorporating quark-gluon plasma formation in OO collisions successfully describe the data. Implications for the interplay between cold nuclear matter effects and color screening in a deconfined quark-gluon plasma are discussed.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://lhcb-glance.cern.ch/alcm/public/analysis/full-details/6994/ (LHCb public pages)