Deuterons at LHC: "snowballs in hell" via hydrodynamics and hadronic afterburner

The deuteron yield in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV is consistent with thermal production at a freeze-out temperature of $T=155$ MeV. The existence of deuterons with binding energy of 2.2 MeV at this temperature was described as “snowballs in hell”. We provide a microscopic explanation of this phenomenon, utilizing relativistic hydrodynamics and switching to a hadronic afterburner at the above mentioned temperature of $T = 155$MeV\mathrm{.}Themeasureddeuteron$p_T$-spectraandcoalescenceparameter$B_2(p_T)$ are reproduced without free parameters, only by implementing experimentally known cross-sections of deuteron reactions with hadrons, most importantly $\pi d\leftrightarrow \pi np$.