Speaker
Description
We investigate the exclusive photoproduction of $J/\psi$-mesons in ultraperipheral
heavy ion collisions in the color dipole approach.
We first test a number of dipole cross sections fitted to inclusive $F_2$-data against the total cross section of exclusive $J/\psi$-production on the free nucleon.
We then use the color-dipole formulation of Glauber-Gribov theory to calculate
the diffractive amplitude on the nuclear target.
The real part of the free nucleon amplitude is taken into account consistent
with the rules of Glauber theory.
We compare our results to recent published and preliminary data
on exclusive $J/\psi$ production in ultraperipheral lead-lead collisions
at $\sqrt{s_{NN}}=2.76 \, \rm{TeV}$ and $\sqrt{s_{NN}} = 5.02 \, \rm{TeV}$.
Especially at high $\gamma A$ energies there is room for additional shadowing corrections, corresponding to triple-Pomeron terms or shadowing from large mass diffraction.
It is based on publication Phys.Rev. C99 (2019) no.4, 044905.
