  We study the impact of magnetic fields generated in relativistic heavy ion
collisions on the decay probability of quarkonium produced in the central
rapidity region. The quark and anti-quark components are subject to mutually
orthogonal electric and magnetic fields in the quarkonium comoving frame. In
the presence of an electric field, quarkonium has finite dissociation
probability. We use the WKB approximation to derive the dissociation
probability. We found that quarkonium dissociation energy, i.e. the binding
energy at which dissociation probability is of order unity, increases with the
magnetic field strength. It also increases with quarkonium momentum in the
laboratory frame due to Lorentz boost of electric field in the comoving frame.
As a consequence, J/Psi in plasma dissociates at lower temperature then it
would be in the absence of a magnetic field. We argue that J/Psi's produced in
heavy-ion collisions at LHC with P_T>9GeV would dissociate even in vacuum. In
plasma, J/Psi dissociation in magnetic field is much stronger due to decrease
of its binding energy with temperature. We discuss the phenomenological
implications of our results.
