Speaker
Eugenio Scapparone
(INFN-Bologna(IT))
Description
Ultra-relativistic heavy ions generate strong electromagnetic fields which offer
the possibility to study gamma-gamma and gamma-nucleus interactions at theLHC in the so called ultra-peripheral collisions (UPC). The J/psi photoproduction in UPC events in sensitive to the gluon distribution of the interacting nuclei, providing information on the nuclear gluon shadowing at Bjorken-x ranging from 10^-5 to 10^-3.
Here we report on ALICE results of J/psi photoproduction measured in Pb-Pb collisions at sqrt(s_NN) = 2.76 where the J/psi has been measured in the muon decay channel with the
Alice Muon Spectrometer in the rapidity range -3.6<y<-2.6; at midrapidity (|y|<0.9) both the leptonic decay channels (ee, mu+mu-)were used. The cross sections are compared with the predictions provided by several event generators.
In addition the cross section for the gamma-gamma --> ee process was studied and compared with the theoretical model expectations.
Author
Eugenio Scapparone
(INFN-Bologna(IT))
