Rapidity dependence of mean transverse momentum fluctuation and decorrelation in baryon-dense medium

TL;DR

This paper investigates how mean transverse momentum fluctuations and decorrelations along rapidity can probe the three-dimensional structure of baryon-rich media and the equation of state, highlighting the robustness of these observables against baryon diffusion.

Contribution

It demonstrates that rapidity-dependent mean transverse momentum fluctuations effectively probe the medium's density profiles and are insensitive to baryon diffusion, providing new insights into baryonic matter properties.

Findings

Mean transverse momentum fluctuation driven by energy and net-baryon-density fluctuations.

Rapidity decorrelation of mean transverse momentum is insensitive to baryon diffusion.

Pronounced splitting in decorrelation between protons and antiprotons.

Abstract

I study the event-by-event fluctuation and rapidity decorrelation of the mean transverse momentum $\spt$, which has recently been proposed as a sensitive probe of the equation of state at finite baryon density. The investigation reveals that, in a baryon-rich medium, the event-by-event fluctuation of the mean transverse momentum is driven by the combined effects of energy-density and net-baryon-density fluctuations. Consequently, the rapidity dependence of this observable provides a promising handle to probe the three-dimensional structure of both energy and baryon density profiles. Previous studies have shown that $\spt$ decorrelation along rapidity is largely insensitive to shear and bulk viscosity; however, its dependence on baryon diffusion, another key transport coefficient in baryonic matter, has not been explored. I find that baryon diffusion has a negligible impact, establishing this observable as a robust probe of the equation of state. Furthermore, I present predictions for identified hadrons and observe a pronounced splitting in the rapidity decorrelation of mean transverse momentum between protons and antiprotons, indicating different transverse flow dynamics for baryons and antibaryons.