Exclusive $\Upsilon$ and $\rho$ (770)$^0$ photoproduction in pPb at $\sqrt { s_{NN}}$ = 5.02TeV with CMS

The first measurements of exclusive ϒ and ρ (770) 0 vector meson photoproduction with the CMS detector at LHC in ultraperipheral proton-lead collisions at sNN=5.02TeV are presented. The ϒ(1S) cross section, which has been measured in the dumuon channel, is consistent with the updated ZEUS ep results at HERA. A fit of function A ( W γ p [GeV]/400) δ to the CMS pPb measurement together with HERA ep and LHCb pp data gives the δ value, consistent with J/ ψ photoproduction results. The obtained result provides a new insight for low-x gluon distribution in protons in an energyrange previously less constrained. The cross section for exclusive photoproduction of ρ (770) 0 has been measured where ρ (770) 0 decays to two pions. The obtained pomeron slope parameter, α ′ = 0.28 ± 0.11(stat) ± 0.12(syst)GeV −2 , is consistent with the ZEUS result and with the Gribov-Regge theory expectation.