Recent ALICE results on $\psi$(2S) production

About

Quarkonia represent a key observable for our understanding of the quark-gluon plasma (QGP) properties, and more generally for the investigation of the QCD color force in a strongly interacting environment. In heavy-ion collisions at LHC energy, significant suppression and regeneration effects were observed and analyzed in detail for the J/$\psi$. An extension of these studies to its first radial excitation, the $\psi$(2S) meson, is particularly relevant. Due to its weaker binding energy, QGP-related effects should exhibit characteristic properties, that are now experimentally investigated by ALICE. In this seminar, after a short general introduction on charmonium modifications in a strongly interacting medium, and a review of relevant lower-energy results for the $\psi$(2S), I will report on a new measurement in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV, that for the first time covers a kinematic region down to zero $p_{\rm T}$. It will be shown that the suppression effects become much stronger than those observed for the J/$\psi$, and that a signal of the regeneration process can be detected also for the $\psi$(2S). Corresponding results for small collision systems will also be presented, looking for possible effects related to the presence of a strongly interacting system created in such interactions.

Refreshments will be served at 10:30. .

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