Probing QCD critical fluctuations from light nuclei production in relativistic heavy-ion collisions

• Kai-Jia Sun (Department of Physics and Astronomy and Shanghai Key Laboratory for Particle Physics and Cosmology)

Large baryon density fluctuations are expected to appear in the matter produced in relativistic heavy-ion collisions if it undergoes a first-order phase transition from the quark-gluon plasma to the hadronic matter. In the case that the density fluctuations can survive final-state interactions during the hadronic evolution and persist until the kinetic freeze-out, they then provide a unique probe to the critical endpoint (CEP), at which the first-order phase transition changes to a smooth crossover, in the QCD phase diagram. In the present study, we demonstrate for the first time that information on the neutron relative density fluctuation at freeze-out can be obtained from the yield ratio of light nuclei in heavy-ion collisions. From recent results on the p, d and 3H yields in central Pb+Pb collisions at the CERN Super Proton Synchrotron (SPS) energies measured by the NA49 Collaboration, we observe a non-monotonic behavior of ∆n as a function of the collision energy with a peak at \sqrt{s_{NN}} = 8.8 GeV, suggesting that the QGP produced at this collision energy may have passed through the CEP during its evolution. https://arxiv.org/pdf/1702.07620.pdf