First LHC results on coherent J/ψ photoproduction in ultra-peripheral Pb-Pb collisions at [formula].

The first LHC measurement on ultra-peripheral heavy-ion collisions was carried out with the ALICE experiment. In this paper, ALICE results on exclusive J/ψ studies in Pb-Pb collisions at [formula], in the rapidity region -3.6 < y < -2.6, are given. The coherent J/ψ cross section was found to be dσcohJ/ψ/dy = 1.00 ± 0.18 (stat)+0.24-0.26 (syst) mb. These studies favour theoretical models that include strong modifications to the nuclear gluon density, also known as nuclear gluon shadowing. [ABSTRACT FROM AUTHOR]