Polarization Dynamics in Paramagnet of Charged Quark-Gluon Plasma

It is commonly understood that the strong magnetic field produced in heavy ion collisions is short-lived. The electric conductivity of the quark-gluon plasma is unable to significantly extend the life time of magnetic field. We propose an alternative scenario to achieve this: with finite baryon density and spin polarization by the initial magnetic field, the quark-gluon plasma behaves as a paramagnet, which may continue to polarize quark after fading of initial magnetic field. We confirm this picture by calculations in both quantum electrodynamics and quantum chromodynamics. In the former case, we find a splitting in the damping rates of probe fermion with opposite spin component along the magnetic field with the splitting parametrically small than the average damping rate. In the latter case, we find a similar splitting in the damping rates of probe quark with opposite spin components along the magnetic field. The splitting is parametrically comparable to the average damping rate, providing an efficient way of polarizing strange quarks by the quark-gluon plasma paramagnet consisting of light quarks.