Measurement of exclusive Upsilon photoproduction in pPb collisions at $\sqrt{s_{NN}} = 5.02$ TeV with the CMS

Abstract

The exclusive photoproduction of $\Upsilon$(1S), $\Upsilon$(2S) and $\Upsilon$(3S) mesons is studied in their leptonic ($\mu^{+}\mu^{-}$) decay modes, in ultraperipheral pPb collisions at $\sqrt{s_{NN}} = 5.02$ TeV. The data was recorded by the CMS experiment corresponding to an integrated luminosity of $32.6$ nb$^{-1}$. The differential cross-section for $\Upsilon$(n) states (n=1,2,3), has been measured as a function of transverse momentum squared $p_{T}^{2}$, and rapidity $y$. The $\Upsilon$(1S) photoproduction cross-section is extracted in the region $|y|<2.2$ as a function of the photon-proton centre-of-mass energies $W_{\gamma p}$, in the range $91 <W_{\gamma p}< 826$ GeV. The measurements are compared to theoretical predictions and to previous measurements.