Flavor-dependent photoproduction in heavyion collisions

Strong electromagnetic fields produced in the non-central heavy-ion collisions can induce vector meson photoproduction.In this paper,we study the photoproduction J/ψandφmesons in the relativistic heavy-ion collision from ultra-peripheral nuclear collisions to peripheral hadronic heavy ion collisions.And then include both initial hadronic production and thermal production in quark-gluon plasma(QGP).We find,for the charm anti-charm bound state J/ψ,the photoproduced J/ψs are mainly in the very low momentum region and clearly exceed the hadronic production.However,considering the thermal production of strange quark anti-quark pairs in QGP produced in relativistic heavy-ion collisions,the photoproducedφis usually smaller than the thermal production and only evident at very peripheral collisions as even their photoproduction is much larger than J/ψ.

Open quantum system approach for heavy quark thermalization

We treat heavy quark as an open quantum system in a hot medium and rederive the stochastic Schrodinger equation(SSE)from the full Schrodinger equation for both heavy quarks and the medium.We apply the SSE to the dynamical evolutions of a heavy quark(as a system)in the static hot medium(as an environment).Heavy quarks interact with the medium via random scatterings,which exchange the momentum and phase factor randomly between two wave functions of the system and the environment.The exchange of momentum and phase factor results in the transition between different eigenstates of the system.These are included via an external stochastic potential in the Hamiltonian of SSE.Stochastic wave functions of a heavy quark are evolved with the stochastic external potential.The mean wave functions and corresponding momentum distributions of heavy quarks are obtained after the ensemble average over a large set of stochastic wave functions.We present the thermalization of heavy quarks in the static medium with different coupling strengths.