Spin polarization dynamics in the non-boost-invariant background

TL;DR

This paper investigates the evolution of spin polarization in a non-boost-invariant hydrodynamic background, revealing effects on observables and comparing results with experimental data and other models.

Contribution

It introduces a hydrodynamic framework for spin dynamics with non-boost-invariant flow, highlighting coupling effects on spin polarization components and their observable consequences.

Findings

Qualitative agreement with experimental rapidity dependence of global spin polarization.

Absence of quadrupole structure at midrapidity in longitudinal polarization.

Observation of non-trivial signals at forward rapidities.

Abstract

Space-time evolution of spin polarization within the framework of hydrodynamics with spin based on de Groot - van Leeuwen - van Weert forms of energy-momentum and spin tensors is studied. Due to the non-boost invariant flow in the system the spin polarization components couple to each other implying some effects on the spin polarization observables. We study transverse-momentum and rapidity dependence of mean spin polarization vector for $\Lambda$ hyperons. Our results show qualitative agreement for rapidity dependence of the global spin polarization with the experiments and other models. The quadrupole structure of the longitudinal component at midrapidity is not found, however, as compared to the results for Bjorken expansion, some non-trivial signal at forward rapidities is observed.