Speaker
Description
Suppression of charmonia is one of the most distinctive signatures of Quark-Gluon Plasma (QGP) in heavy-ion collisions. Suppression can also take place in hadron-nucleus collisions due to cold nuclear matter (CNM) effects where the presence of QGP is not expected. The hadron-nucleus collisions are therefore important as they help to disentangle the effects of the QGP from those due to CNM. Charmonium production in hA collisions at fixed-target energies is sensitive to the effects of nPDF and the partonic energy loss in nuclear matter. It is conveniently complemented by the well-known Drell-Yan process.
The double differential ($x_{\rm F}$, $p_{\rm T}$) cross-sections of J/$\psi$ production and Drell-Yan process have been measured by the COMPASS collaboration in hA collisions at $\sqrt{s} = 18.9$ GeV. A negative pion beam with a momentum of 190 GeV/c was impinging on ammonia, aluminum, and tungsten targets. The preliminary results for the ratios of heavy to light targets for both charmonia production and Drell-Yan show suppression towards high $x_{\rm F}$. A dependence with $p_{\rm T}$ is also investigated, which might indicate the presence of energy loss effects. COMPASS findings on the nuclear effects of the J/$\psi$ production and Drell-Yan process will be presented. The results will be compared to the available fixed-target and collider measurements in order to explore scaling behavior and energy dependence and will be followed by the comparison with theoretical model predictions.
