Charmonium production from small to large systems at LHCb

Quarkonium production is a powerful probe of heavy-quark interactions with nuclear matter, and one of the proposed observables for this purpose is the ψ(2S)-to-J/ψ cross-section ratio. LHCb has recently measured this ratio in Run 2 data as a function of multiplicity in pp and pPb collisions, and as a function of centrality in PbPb collisions. Results in pp and forward pPb show a multiplicity dependence consistent with co-movers, while backward Pbp is flat. The cross-section ratio in PbPb is in agreement with previous results and best described by the TAMU transport model. With its Run 3 upgrades, including the SMOG2 fixed-target system, LHCb can now perform higher-precision PbPb studies, explore new collision systems, and thereby improve our understanding of the medium created in heavy-ion collisions.