Speaker
Description
The powerful photon fluxes of relativistic nuclei provide the possibility to study photonuclear and two-photon interactions in ultra-peripheral collisions (UPC), where the nuclei do not overlap and no strong nuclear interactions occur. Within the Vector Meson Dominance Model (VDM), the rho0 contribution dominates the QCD part of the photon structure function. The gamma+A → rho0+A process in heavy-ion UPC is an excellent tool to test the black disk regime, where the target nucleus appears like a black disk and the total rho0+A cross section reaches its limit. RHIC and first LHC results have deviated from some Glauber+VDM calculations, which thus call for new data. ALICE reports the first measurements of coherent rho photoproduction accompanied by electromagnetic dissociation (EMD) with data taken at sqrt(s_NN ) =5.02 TeV. The rapidity-dependent cross section
of coherent rho0 photoproduction is measured and it is compared to theoretical models. In addition, a resonance-like structure around 1.7 GeV/𝑐^2 is observed.
