\psi(2S) production as a function of charged-particle multiplicity in pp collisions at $\sqrt{s}$= 13 TeV and p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$= 8.16 TeV with ALICE at the LHC

TL;DR

This study measures how the production of a(2S) charmonium states varies with charged-particle multiplicity in proton-proton and proton-lead collisions at the LHC, providing insights into multiparton interactions.

Contribution

It presents the first detailed measurement of a(2S) yields as a function of multiplicity in small collision systems at the LHC, comparing results to theoretical models.

Findings

a(2S) yield increases with multiplicity in pp and p--Pb collisions.

The a(2S)-over-J/a ratio varies with multiplicity, indicating different production mechanisms.

Results are consistent with models including multiparton interactions.

Abstract

The self-normalised $\psi(2S)$ yields as a function of charged-particle multiplicity in pp collisions at $\sqrt{s}$ = 13 TeV and p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$= 8.16 TeV, using the ALICE detector at the CERN LHC, are reported in these proceedings. This measurement represents one of the main tools to understand the role of multiparton interactions and their influence on charmonium production in small systems, i.e pp and pA collisions. The ratio of $\psi(2S)$-over-J/$\psi$ as a function of charged-particle multiplicity is also presented for both pp and p--Pb collisions. The comparison to theoretical calculations is reported.