Abstract
Photonuclear reactions are induced by the strong electromagnetic field generated by ultrarelativistic heavy-ion collisions. These processes have been extensively studied in ultraperipheral collisions, where the impact parameter is larger than twice the nuclear radius. In recent years, the observation of coherent J/ψ photoproduction at very low transverse momentum has been claimed in nucleus−nucleus (A−A) collisions with nuclear overlap, based on the measurement of an excess in the J/ψ yield with respect to hadroproduction expectations. Such quarkonium measurements can help to constrain the nuclear gluon distribution at low Bjorken-x and high energy. The photoproduced quarkonium is expected to preserve the polarization of the incoming photon due to the s-channel helicity conservation. In this contribution, we report on the new preliminary measurements of the y-differential cross section and the first polarization analysis of coherently photoproduced J/ψ in peripheral Pb−Pb collisions with the ALICE detector at forward rapidity in the dimuon decay channel. Comparison with models will be shown when available.