Apr 23 – 27, 2023
JMS Aster Plaza
Asia/Tokyo timezone

Effect of event-by-event fluctuations on light-nuclei yield ratio

Apr 26, 2023, 2:40 PM
Multi-Purpose Studio, 2nd Floor (JMS Aster Plaza)

Multi-Purpose Studio, 2nd Floor

JMS Aster Plaza

Oral QCD phase diagram and extreme states Parallel Session C


Koichi Murase (Yukawa Institute for Theoretical Physics, Kyoto University)


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, $N_tN_p/N_d^2$ (with $N_t$, $N_p$, and $N_d$ being triton, proton, and deuteron numbers, respectively) [1], 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 [2] and the event-by-event fluctuations coming from the initial state.

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 find that the event-by-event fluctuations increase the yield ratio, where the value takes maximum at a particular hot-spot number $n$ depending on the fireball size. The effective dimension of the fluctuations also affects the amount of increase. These understandings of the yield ratio will be important in analyzing the results of future realistic dynamical calculations.

[1] K. J. Sun, L. W. Chen, C. M. Ko and Z. Xu, Phys. Lett. B 774 (2017), 103-107.
[2] S. Wu, K. Murase, S. Tang and H. Song, Phys. Rev. C 106 (2022), 034905.

Theory / experiment Theory

Primary authors

Koichi Murase (Yukawa Institute for Theoretical Physics, Kyoto University) Shanjin Wu (Lanzhou University, Peking University)

Presentation materials