Speaker
Description
In Ultra-Peripheral Collisions (UPC), two nuclei pass close to each other
at an impact parameter greater than the sum of their radii; in such
collisions hadronic processes are strongly suppressed, while γ interactions
are enhanced with respect to minimum-bias collisions.
Photoproduction of vector mesons in UPC is a powerful tool to probe the
nuclear gluon distribution in the nucleus, for which there is considerable
uncertainty in the low-x region.
The ALICE collaboration has published measurements of UPC J/ψ and ψ(2S) photoproduction in LHC Run 1 at forward (J/ψ) and at mid-rapidity.
In addition 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, together
with results on photoproduction of ρ0 from Run 1 and 2 and a comparison
with theoretical models.
