Role of bulk viscosity in deuteron production in ultrarelativistic nuclear collisions

We use a Bayesian-calibrated multistage viscous hydrodynamic model to explore deuteron yield, mean transverse momentum and flow observables in Pb-Pb collisions at the Large Hadron Collider. We explore theoretical uncertainty in the production of deuterons, including (i) the contribution of thermal deuterons, (ii) models for the subsequent formation of deuterons (hadronic transport vs coalescence), and (iii) the overall sensitivity of the results to the hydrodynamic model, in particular to bulk viscosity, which is often neglected in studies of deuteron production. Using physical parameters set by a comparison to only light hadron observables, we find good agreement with measurements of the mean transverse momentum (pT) and elliptic flow v2 of deuterons; however, tension is observed with experimental data for the deuteron multiplicity in central collisions. The results are found to be sensitive to each of the mentioned theoretical uncertainties, with a particular sensitivity to bulk viscosity, indicating that the latter is an important ingredient for an accurate treatment of deuteron production.

Automated summary

In this study, a Bayesian-calibrated multistage viscous hydrodynamic model was used to investigate the deuteron yield, mean transverse momentum, and flow observables in Pb-Pb collisions at the Large Hadron Collider. The theoretical uncertainties in deuteron production, including the contribution of thermal deuterons, models for the subsequent formation of deuterons, and the sensitivity to the hydrodynamic model, were explored. The results showed that each of these theoretical uncertainties had a significant impact on the results, with bulk viscosity being particularly important for an accurate treatment of deuteron production.