Coulomb nuclear interference effect in dipion production in ultraperipheral heavy ion collisions

Abstract

We study exclusive $\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ pair production near $\ddot{I}{}^0$ resonance peak in ultraperipheral heavy ion collisions. Pion pair can either be produced via two photon fusion process or from the decay of $\ddot{I}{}^0$ in photon-nuclear reaction. At very low pair transverse momentum, the electromagnetic and nuclear amplitudes become comparable. We show that the Coulomb nuclear interference amplitude gives rise to sizable $\cos \ddot{I}•$ and $\cos 3\ddot{I}•$ azimuthal asymmetries, which can be used to constrain the phase of the dipole-nucleus scattering amplitude.

9 pages, 3 figures