Speaker
Description
We calculate the cross section for the heavy quark $(Q)$ production through gluon $(g)$ fusion process $g+g\to Q+\bar{Q}$ in the presence of a weak external magnetic field $(B)$. Several studies have estimated the $B$ field strength in non-central heavy-ion collisions to be $eB\sim m_\pi^2\sim 10^{18},\text{G}$. Thus, for heavy flavour mass $m_Q$, the inequality $m_Q^2 \gg eB$ is largely satisfied, justifying the weak field approximation. The fermion propagator in a weak magnetic field is treated using Schwinger’s proper-time formalism. Owing to the hierarchy of scales ($m_Q^2 \gg eB$), we neglect the effects of the magnetic field on the quark and antiquark spinors. Since the magnetic field breaks rotational invariance, the cross section becomes anisotropic and depends on the relative orientation between the magnetic field and the incoming gluons and the outgoing heavy quarks. This has interesting signatures on heavy quark observables, carrying information about the initial stage B fields produced in relativistic heavy ion collisions.