Spin polarization induced by the hydrodynamic gradients

• Published in: The journal of high energy physics Vol. 2021; no. 7; pp. 1 - 19
• Main Authors: Liu, Shuai Y. F., Yin, Yi
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.07.2021; Springer Nature B.V; SpringerOpen
• Subjects: Classical and Quantum Gravitation; Electrons; Elementary Particles; Heavy ions; High energy physics; Ionic collisions; Phase Diagram of QCD; Physics; Physics and Astronomy; Polarization (spin alignment); Quadrupoles; Quantum Field Theories; Quantum Field Theory; Quantum Physics; Quark-Gluon Plasma; Regular Article - Theoretical Physics; Relativity Theory; Shear strength; String Theory; Symmetry; Vorticity; Quark-Gluon Plasma; Phase Diagram of QCD
• ISSN: 1029-8479; 1029-8479
• DOI: 10.1007/JHEP07(2021)188

A bstract We systematically analyze the effects of the derivatives of the hydrodynamic fields on axial Wigner function that describes the spin polarization vector in phase space. We have included all possible first-order derivative contributions that are allowed by symmetry and compute the associated transport functions at one-loop using the linear response theory. In addition to reproducing known effects due to the temperature gradient and vorticity, we have identified a number of potentially significant contributions that are overlooked previously. In particular, we find that the shear strength, the symmetric and traceless part of the flow gradient, will induce a quadrupole for spin polarization in the phase space. Our results, together with hydrodynamic gradients obtained from hydrodynamic simulations, can be employed as a basis for the interpretation of the Λ (anti-Λ) spin polarization measurement in heavy-ion collisions.