Quark polarization in a viscous quark-gluon plasma

Abstract

Quarks produced in the early stage of non-central heavy-ion collisions could develop a global spin polarization along the opposite direction of the reaction plane due to the spin-orbital coupling via parton interaction in a medium that has finite longitudinal flow shear along the direction of the impact parameter. We study how such polarization evolves via multiple scattering in a viscous quark-gluon plasma with an initial laminar flow. The final polarization is found to be sensitive to the viscosity and the initial shear of local longitudinal flow.

Electromagnetic fields and anomalous transports in heavy-ion collisions—a pedagogical review

“…(1) The noncentral heavy-ion collisions can generate fluid vorticity in the interaction region [252][253][254][255][256][257][258]. The fluid vorticity can also induce anomalous transports, generally called the chiral vortical effect (CVE) [20][21][22] (earlier suggestion is given in Ref.…”

Polarization of massive fermions in a vortical fluid

“…In non-central high-energy heavy-ion collisions, the large orbital angular momentum present in the colliding system can lead to non-vanishing local vorticity in the hot and dense fluid [1][2][3][4][5][6]. The vorticity induced by global orbital angular momentum in the fluid can be considered as local rotational motion of particles [3,4,7,8].…”

Global Λ polarization in high energy collisions

“…The drastic thermal motion of particles will decrease the quark polarization rate, which according to Ref. [11] is inversely proportional to the collision energy. On the other hand, simulating results by a multi-phase transport (AMPT) model has shown that the averaged classical vorticity decreases with the collision energy [36,37], which, of course, leads to the decline of global polarization.…”

“…Afterwards, more experimental research was launched continuously, including nucleon collisions and heavy ion collisions [3][4][5][6][7][8][9]. Theoretical studies have also been under way synchronously with the experiments [10][11][12][13][14][15][16][17][18][19].…”

“…From the partonic micro-perspective, the initial angular momentum is transferred to the partons through the interaction of spin-orbit coupling in viscous QGP [11], and then the global polarized quarks are recombined into hadrons, in which the Thomas precession of the quark spin was applied [25].…”