Directed flow in a baryonic fireball

TL;DR

This paper introduces a new initial condition model for baryon deposition in a tilted fireball, successfully describing directed flow of hadrons and baryon-antibaryon splitting, and highlights the potential of future measurements to constrain baryon diffusion.

Contribution

It proposes a novel baryon deposition ansatz coupled with a tilted fireball model, improving the description of directed flow and baryon-antibaryon splitting in heavy-ion collisions.

Findings

Successfully describes directed flow of identified hadrons

Reproduces baryon-antibaryon splitting of directed flow

Suggests future measurements can constrain baryon diffusion coefficient

Abstract

Directed flow of identified hadrons in a baryon rich fireball is an interesting observable as it is expected to probe several physics aspects: the initial three dimensional baryon profile in the thermalised fireball that can be treated as an input for the hydrodynamic evolution, the nature of baryon dissipation current and baryon transport coefficients, the QCD equation of state at finite baryon densities as well as the nature of phase transition between the quark gluon and hadronic phases. Particularly, the mid-rapidity slope of the rapidity dependence of directed flow of protons have been proposed as a sensitive observable to several of these physics aspects while a consistent description of the splitting in directed flow of baryon and its anti-particle has been a challenge. In this work, we propose a suitable ansatz of the initial condition for baryon deposition. When such a baryon deposition ansatz is coupled to a tilted fireball, we manage to find parameter space that can describe the directed flow of identified hadrons including the elusive baryon antibaryon splitting of directed flow. Further, we demonstrate that future measurements of baryon antibaryon directed flow at larger rapidities have the potential to constrain the baryon diffusion coefficient.