  We compute the probability of $J/\psi$ production from the interaction
between $\eta_c$ and the strong magnetic field generated in relativistic heavy
ion collisions. The computation is first carried out in the heavy quark
effective model, in which the M1 radiative transition is considered. Then we
investigate the transition in the framework of non-relativistic heavy hadron
chiral perturbation theory and show that the polarization of $J/\psi$ produced
by this process is parallel to the direction of magnetic field and thus
perpendicular to the reaction plane. The transition probability obtained in
both approaches is of order $2\times 10^{-4}$.

High Energy Physics - Phenomenology