Kayman J. Gonçalves, State University of Campinas, Brazil

"Polarization of vector mesons in non-equilibrium hydrodynamics with spin"

Abstract: One of the most interesting developments in the investigation of quark-gluon plasma was the discovery that the vorticose fluid created in heavy ion collisions polarizes Lambda baryons and aligns spin of quarkonia (bound quark-antiquark states) and vector mesons [1]. This opened a new deep field of investigation, since the interaction of spin and vorticity in systems close to local equilibrium is not understood even on a conceptual level. Here, we argue that spin alignment of hadrons of spin 1 and higher provide a unique window into the study of hydrodynamics with spin, because it is capable to probe non-equilibrium between spin density and vorticity. This happens because most of the full 3X3 density matrix is in principle accessible experimentally, and non-zero off-diagonal matrix elements can be directly linked to such non-equilibrium. We illustrate this using a coalescence model for light vector mesons [2] as well as a potential model for quarkonia, and compare our calculations to experimental data [3].

[1] F Becattini, M. Lisa, 2003.03640
[2] Kayman J. Gonçalves, Giorgio Torrieri, Phys.Rev.C 105 (2022) 3,
034913, e-Print: 2104.12941
[3] Paulo de Moura, Kayman J. Gonçalves, Giorgio Torrieri 2305.02428