Measurement of exclusive ρ 770 0 photoproduction in ultraperipheral pPb collisions at s NN = 5.02 Te

Abstract

Exclusive ${{{\rho }_{}^{}}_{}^{}\left(770\right){}_{}^{}}^0$ photoproduction is measured for the first time in ultraperipheral pPb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=5.02\text{Te}$ with the CMS detector. The cross section $\sigma ({\gamma }_{}^{}p\to {{{\rho }_{}^{}}_{}^{}\left(770\right){}_{}^{}}^{0}p)$ is $11.0\pm 1.4\text{(stat)}\pm 1.0\text{(syst)}$ $\mu$ b at $⟨W_{{\gamma }_{}^{}p}⟩=92.6\text{Ge}$ for photon-proton centre-of-mass energies $W_{{\gamma }_{}^{}p}$ between 29 and $213\text{Ge}$ . The differential cross section $d\sigma /d\left|t\right|$ is measured in the interval $0.025<\left|t\right|<1{\text{Ge}}^2$ as a function of $W_{{\gamma }_{}^{}p}$ , where t is the squared four-momentum transfer at the proton vertex. The results are compared with previous measurements and theoretical predictions. The measured cross section $\sigma ({\gamma }_{}^{}p\to {{{\rho }_{}^{}}_{}^{}\left(770\right){}_{}^{}}^{0}p)$ has a power-law dependence on the photon-proton centre-of-mass, consistent with electron-proton collision measurements performed at HERA. The $W_{{\gamma }_{}^{}p}$ dependence of the exponential slope of the differential cross section $d\sigma /d\left|t\right|$ is also measured.