  Ultra-peripheral Pb-Pb collisions, in which the two nuclei pass close to each
other, but at an impact parameter greater than the sum of their radii, provide
information about the initial state of nuclei. In particular, heavy vector
meson production, where the particle mass sets a hard scale, proceeds in such
collisions by photon-gluon interactions, and gives access to nuclear PDFs. The
ALICE collaboration has published measurements of J/psi and psi(2S)
photoproduction in ultra-peripheral collisions in LHC Run 1 at forward (J/psi)
and mid-rapidity, and has obtained a substantially larger data set in 2015 from
LHC Run 2, allowing much more detailed studies of the production mechanism to
be performed. In particular, the increased energy and more detailed
measurements in the forward region in Run 2 give access to significantly lower
values of Bjorken-x than in previous studies. In this talk, the latest
available results from Run 2 will be given.
