Gießen 2024 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 22: Heavy-Ion Collisions and QCD Phases IV
HK 22.1: Gruppenbericht
Dienstag, 12. März 2024, 15:45–16:15, HBR 62: EG 05
Recent developments in dissipative spin hydrodynamics — •Masoud Shokri1, Annamaria Chiarini1, Julia Sammet1, Nils Sass1, David Wagner1, Ashutosh Dash1, Enrico Speranza2, Nora Weickgenannt3, Hannah Elfner1, and Dirk H. Rischke1 — 1Goethe University, Frankfurt am Main, Germany — 2IPhT, Saclay, France — 3CERN, Switzerland
Transport equations for particles with spin can be rigorously derived from quantum kinetic theory in an expansion in Planck's constant. At zeroth order, the standard Boltzmann equation is recovered. At first order, a nonlocal contribution to the collision term is found, which enables the mutual conversion of orbital angular momentum into spin and thus provides a microscopic mechanism for the time-honored Barnett effect. The method of moments is applied to derive second-order dissipative spin hydrodynamics. Investigating this theory in the linear regime confirms the need for a second-order theory. We computed the transport coefficients of this theory and found that spin diffusion happens on rather short time scales, while spin degrees of freedom approach local equilibrium on rather long time scales. This separation of time scales allows a simplification of the expression for the polarization vector and a numerical evaluation without explicitly solving the equations of motion for the spin degrees of freedom. While we find qualitative agreement with experimental data, a quantitatively reliable calculation requires the development of numerical simulations for spin hydrodynamics. Finally, an outlook for further theoretical and phenomenological developments is given.
Keywords: Hydrodynamic models; Relativistic heavy-ion collisions; Quark-gluon plasma; Polarization; Spin