Speaker
Description
Charmonium mesons are among the most important probes of deconfined QCD matter. A complete understanding of their production and interaction with the medium created in the collision is necessary to disentangle genuine hot-matter effects from cold nuclear matter effects. To achieve this, charmonium production must be measured in different collision systems over a wide energy range. Fixed-target collisions at LHCb, enabled by the SMOG2 system, complement studies performed in collider mode and provide access to kinematic regions not explored by other fixed-target experiments. In Run 2, the LHCb collaboration provided results on $J/\psi$-to-$D_0$ and $\psi(2S)$ -to-$J/ \psi$ ratios in $p$ Ne and PbNe collisions at $\sqrt{s_NN} = 68.5$ GeV. In Run 3 the SMOG2 system has so far enabled an expanded set of targets, including He, Ne, Ar, $\mathrm{O}_2$, $\mathrm{D}_2$ and $\mathrm{H}_2$, the latter serving as a proxy for $pp$ collisions at $\sqrt{s_{NN}} = 113$ GeV. Here we present the first LHCb fixed-target heavy-flavor results from Run 3, with a focus on charmonia, and discuss the prospects for upcoming analyses aimed at improving the precision of and extending the Run 2 results. In addition, we present the first results on the determination of centrality classes in lead-target datasets from Run 3, as this variable is crucial for most heavy-ion physics analyses. Taken together, these results highlight the unique opportunities offered by the LHCb fixed-target programme for studying quarkonium production and nuclear matter effects, and advancing our understanding of QCD matter under extreme conditions.
| Track | Heavy Ions |
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