Recent results on ultra-peripheral collisions at the LHC with ALICE

Hosokawa, Ritsuya; on behalf of the ALICE collaboration,

doi:10.22323/1.380.0254

Abstract

Ultra-peripheral collisions (UPCs) of relativistic heavy-ion collisions provide a unique opportunity to study photon induced interactions at the LHC in new kinematic regimes. The ALICE experiment has measured the coherent photo-nuclear production of

$\rho^{0}$ and

$J/\psi$ vector mesons in UPCs. The measurement of

$\rho$ vector meson is an excellent tool to study nuclear shadowing effects and the approach to the black-disc limit of QCD, while the

$J/\psi$ measurement is also a good tool to study nuclear shadowing and saturation effects at low-x. In this contribution, recent results obtained with the data from LHC Run2 will be presented. The first measurement of the cross section of

$\rho^{0}$ mesons in Xe--Xe at

$\sqrt{s_{\mathrm{NN}}}$ = 5.44 TeV and Pb--Pb UPCs at

$\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV, and the cross section and t-dependence of

$J/\psi$ mesons in Pb--Pb UPCs at

$\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV will be reported. These results are compared with various model predictions in order to improve our phenomenological understanding of UPCs.