# Microscopic study of deuteron production in PbPb collisions at $\sqrt{s}=2.76\phantom{\rule{0.28em}{0ex}}\mathrm{TeV}$ via hydrodynamics and a hadronic afterburner

Oliinychenko, Dmytro (Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, California 94720, USA) ; Pang, Long-Gang (Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, California 94720, USA) (Physics Department, University of California, Berkeley, California 94720, USA) ; Elfner, Hannah (Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strasse 1, 60438 Frankfurt am Main, Germany) (Institute for Theoretical Physics, Goethe University, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany) (GSI Helmholtzzentrum für Schwerionenforschung, Planckstr. 1, 64291 Darmstadt, Germany) ; Koch, Volker (Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, California 94720, USA)

12 April 2019

Abstract: The deuteron yield in Pb+Pb collisions at $\sqrt{{s}_{NN}}=2.76\phantom{\rule{0.28em}{0ex}}\mathrm{TeV}$ is consistent with thermal production at a freeze out temperature of $T=155\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$. The existence of deuterons with binding energy of 2.2 MeV at this temperature was described as “snowballs in hell” [P. Braun-Münzinger, B. Dönigus, and N. Löher, CERN Courier, August 2015]. We provide a microscopic explanation of this phenomenon, utilizing relativistic hydrodynamics and switching to a hadronic afterburner at the above-mentioned temperature of $T=155\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$. The measured deuteron ${p}_{T}$ spectra and coalescence parameter ${B}_{2}\left({p}_{T}\right)$ are reproduced without free parameters, only by implementing experimentally known cross sections of deuteron reactions with hadrons, most importantly $\pi d↔\pi np$.

Published in: Physical Review C 99 (2019)