Event-by-event fluctuations on light-nuclei production in coalescence model

We investigate how the event-by-event fluctuations of the final-state distribution function of nucleons physically affect the yield ratio of light nuclei based on the coalescence model.

The yield ratio of light nuclei, N_t N_p / N_d² (with N_t, N_p, and N_d being triton, proton, and deuteron numbers, respectively), is one of the observables suggested for a possible signal of the critical point of quantum chromodynamics (QCD). Based on the analyses with idealized setups, the yield ratio is known to be sensitive to the two-point neutron correlation and thus to the critical correlations. However, it is non-trivial how the yield ratio is affected by the other contributions in realistic setups of heavy-ion collisions, such as anisotropic flows and the initial-state fluctuations.

In this talk, we establish a qualitative understanding of how event-by-event fluctuations affect the yield ratio. We model the "single-event" distribution f(x, p) by a superposition of n-Gaussian hot spots in phase space and randomize the positions and magnitudes of the hot spots from event to event. We obtain analytical formulae for the yields of light nuclei and related ratios under this setup. We investigate how each feature of the event-by-event distribution affects the yield ratio. We also discuss the scale separation between the critical correlations and short-range thermal fluctuations using two different sizes of hot spots.