Exploring the Nuclear-Shape Phase Transition in Ultrarelativistic129Xe+129XeCollisions at the LHC

Abstract

The shape phase transition for certain isotope or isotone chains, associated with the quantum phase transition of finite nuclei, is an intriguing phenomenon in nuclear physics. A notable case is the Xe isotope chain, where the structure transits from a 𝛾-soft rotor to a spherical vibrator, with the second-order shape phase transition occurring in the vicinity of 128–130Xe. In this Letter, we focus on investigating the 𝛾-soft deformation of 129Xe associated with the second-order shape phase transition by constructing novel correlators for ultrarelativistic 129Xe+129Xe collisions. In particular, our iEBE-VISHNU model calculations show that the correlation between elliptic flow 𝑣2 and mean transverse momentum [𝑝𝑇], denoted as 𝜌2, as well as the [𝑝𝑇] fluctuation Γ𝑝𝑇, which were previously used to claim the evidence of the rigid triaxial deformation of 129Xe, can also be well explained by the 𝛾-soft deformation of 129Xe. We further propose two novel correlators 𝜌4,2 and 𝜌2,4, which carry nontrivial higher-order correlations and show unique capabilities to distinguish between the 𝛾-soft and the rigid triaxial deformation of 129Xe in 129Xe+129Xe collisions at the LHC. The present study provides a novel way to explore the second-order shape phase transition of finite nuclei with ultrarelativistic heavy ion collisions.