J/psi production in ultra-peripheral proton-lead and lead-lead collisions with CMS

This thesis reports on photoproduction of exclusiveJ=ymesons in ultra-peripheralPbPb and pPb collisions atpsNN=2:76 TeV, and 5.02 TeV, respectively, from theCMS experiment at the LHC. For PbPb collisions, there is a correlation between thedirections of the producedJ=yand the neutron emitted by the struck nucleus. ForJ=ymesons withpT>100 MeV/c, the ratio of thepTdistributions forJ=yis moving inthe opposite direction as the neutrons emitted from the target nucleus to those forJ=yis moving in the same direction as the neutrons, suggests significant shadowing in thelead nucleus.For pPb collisions, the distributions of theJ=ys in transverse momentum have a sim-ilar form to previous measurements at HERA. The averagepTincreases with thephoton-proton center of mass energyW. This implies that the spatial distribution of thegluons within the proton depends upon the gluon momentum. The cross section alsoincreases asWincreases from 57 to 439 GeV implying that the proton become moreand more opaque to photons as the photon energy increases. Parametrizing the growthof the cross section by the forms(W)μWdyields a value ofd=0:6360:063. Thisresult is consistent with the world average and has a precision comparable to otherexperiments