Semiclassical treatment of bottomonium suppression and regeneration in $p+{ m Pb}$ collisions

We study bottomonium suppression in $p+ {\rm Pb}$ relative to $p+p$ collisions at center-of-mass energies of $\sqrt{s_{NN}}= 5.02$ and 8.16~TeV. Specifically, we combine cold nuclear matter effects (nuclear modifications of the parton densities, energy loss and momentum broadening) with those from hot nuclear matter (suppression and regeneration) by implementing the formation of a quark-gluon plasma in hydrodynamic simulations. Bottomonium transport in the quark-gluon plasma is evaluated semiclassically, employing two different reaction rates. The first includes quasi-free inelastic scattering and gluo-dissociation employing a perturbative coupling to the medium. The second is based on in-medium $T$-matrix calculations where the input potential is constrained by lattice quantum chromodynamics to extract the bottomonium masses and dissociation rates. These semiclassical results are compared to previous calculations in an open quantum systems approach and to the experimental data. Predictions for $χ_b$ suppression at $\sqrt{s_{NN}} = 8.16$~TeV are also presented.

💡 Research Summary

This paper presents a comprehensive study of bottomonium (Υ) suppression and regeneration in proton‑lead (p+Pb) collisions at the LHC energies √sₙₙ = 5.02 TeV and 8.16 TeV. The authors construct a three‑stage framework that sequentially incorporates (i) cold‑nuclear‑matter (CNM) effects, (ii) the formation and hydrodynamic evolution of a short‑lived quark‑gluon plasma (QGP), and (iii) the semiclassical transport of bottomonium states through the expanding medium.

In the first stage, nuclear parton‑distribution‑function (nPDF) modifications are implemented using the EPPS21 set, which accounts for shadowing and antishadowing in the lead nucleus. Coherent initial‑state energy loss and transverse‑momentum broadening are added following the formalism of Refs.