Speaker
Ruchi Chudasama
(Bhabha Atomic Research Centre (IN))
Description
Results on exclusive photoproduction of $\Upsilon$ states in ultra-peripheral collisions (UPC) of protons and ions at CMS are presented, which provides a clean probe of the gluon distribution at small values of parton fractional momenta $x~10^{-4}-10^{-3}$. The three $\Upsilon$ states (1S, 2S, 3S) are measured in the dimuon decay channel, on top of the photon-photon $ \rightarrow$ $\mu\mu$ QED continuum, in pPb collisions at $\sqrt{s_{NN}}=5.02$~TeV (for integrated luminosity of $L_{int} = 35$ nb$^{-1}$) and in pp at $\sqrt{s}=7$ TeV ($L_{int} = 5.24$ fb$^{-1}$). The total $\Upsilon$ photoproduction cross sections as well as the t-differential distributions are compared to various theoretical predictions. The impact of these data on the central values and uncertainties of the low-x gluon distribution will be assessed.
| On behalf of collaboration: | CMS |
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Primary author
Ruchi Chudasama
(Bhabha Atomic Research Centre (IN))
