Evolution of $\Lambda$ polarization in the hadronic phase of heavy-ion collisions

Abstract

Using the AMPT + MUSIC+UrQMD hybrid model, we study the global and local spin polarizations of $\Lambda$ hyperons as functions of the freeze-out temperature of the spin degree of freedom in the hadronic phase of Au+Au collisions at $\sqrt{s_{NN}}=19.6$ GeV. Including contributions from both the thermal vorticity and thermal shear of the hadronic matter, we find that, with the spin freeze-out temperature dropping from the hadronization temperature of 160 MeV to 110 MeV at the kinetic freeze-out, both the global and local spin polarizations of $\Lambda$ hyperons due to the thermal vorticity decrease by a factor of two, while those due to the thermal shear decrease quickly and become negligibly small at 140 MeV. Our results suggest the importance of understanding the dynamical evolution of the spin degree of freedom in the hadronic stage in relativistic heavy-ion collisions.

5 pages, 3 figures, references updated

References in corpus (16)

• Elliptic and triangular flow in event-by-event (3+1)D viscous hydrodynamics
• Collective longitudinal polarization in relativistic heavy-ion collisions at very high energy
• Global quark polarization in non-central $A+A$ collisions
• Shear-induced spin polarization in heavy-ion collisions
• Local polarization and isothermal local equilibrium in relativistic heavy ion collisions
• Spin-thermal shear coupling in a relativistic fluid
• Global $\Lambda$ Polarization in high energy collisions
• Flow Vorticity in Peripheral High Energy Heavy Ion Collisions
• Lambda hyperon polarization in relativistic heavy ion collisions from the chiral kinetic approach
• Spin polarization induced by the hydrodynamic gradients
• Derivation of the nonlocal collision term in the relativistic Boltzmann equation for massive spin-1/2 particles from quantum field theory
• Global polarization of $\Xi$ and $\Omega$ hyperons in Au+Au collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV
• From Kadanoff--Baym to Boltzmann equations for massive spin-1/2 fermions
• Reexamination of local spin polarization beyond global equilibrium in relativistic heavy ion collisions
• A hydrodynamic study of hyperon spin polarization in relativistic heavy ion collisions
• $\Lambda$ polarization in peripheral collisions at moderate relativistic energies

Cited by in corpus (11)

• Local and global polarization of $\Lambda$ hyperons across RHIC-BES energies: the roles of spin hall effect, initial condition and baryon diffusion
• Polarization phenomenon in heavy-ion collisions
• Quantum kinetic theory for dynamical spin polarization from QED-type interaction
• $\Lambda /\bar{\Lambda }$ Polarization and Splitting Induced by Rotation and Magnetic Field
• Analytic solutions of relativistic dissipative spin hydrodynamics with radial expansion in Gubser flow
• Hydrodynamic helicity polarization in relativistic heavy ion collisions
• Spin evolution of massive fermion in QED plasma
• Quantum kinetic theory for spin transport of quarks with background chromo-electromagnetic fields
• Polarization in heavy ion collisions: a theoretical review
• Global $\Lambda$ polarization in heavy-ion collisions at high baryon density
• Practical considerations for the effect of finite coverage on the azimuthal dependence of global spin alignment