Speaker
Description
The study of vector meson photoproduction in ultraperipheral collisions (UPCs) offers a powerful probe of gluon dynamics in heavy nuclei. In UPCs, photons can interact with the nucleus coherently (involving the entire nucleus) or incoherently (with individual constituents). While coherent processes provide insight into the average gluon density, incoherent photoproduction is uniquely sensitive to the local gluon density fluctuations at both nucleonic or subnucleonic levels. Moreover, vector mesons of different masses probe different hard scales, offering complementary sensitivity to nonlinear QCD effects and potential gluon saturation phenomena.
In this talk, we present recent CMS results on vector meson photoproduction in UPCs, including the first observations of coherent $\phi$ and $\Upsilon(1S)$ photoproduction and the first energy-dependent measurements of incoherent $J/\psi$ cross sections. The results will be compared with state-of-the-art theoretical models, offering new insights into gluon density fluctuations and enhancing our understanding of nuclear gluon distributions and QCD saturation.
