Diffraction and ultraperipheral collisions at ALICE

TL;DR

This paper reports measurements of J/psi and rho_0 photoproduction in ultraperipheral Pb+Pb collisions at the LHC, providing insights into nuclear gluon shadowing and diffraction phenomena.

Contribution

First measurement of J/psi photoproduction cross section in ultraperipheral Pb+Pb collisions at the LHC, supporting models with nuclear gluon shadowing.

Findings

J/psi cross section agrees with models including nuclear gluon shadowing

Results on rho_0 photoproduction are consistent with theoretical expectations

Studies on exclusive J/psi and diffraction in pp collisions are discussed

Abstract

The ALICE experiment measured J/psi photoproduction in Pb+Pb ultraperipheral collisions at sqrt(s_NN) = 2.76 TeV at forward and central rapidity. The coherent J/psi cross section is found to be in good agreement with those models which include nuclear gluon shadowing consistent with EPS09 parametrization. Results on rho_0 photoproduction in ultra-peripheral Pb+Pb collisions are also briefly discussed. Studies on exclusive J/psi in p+Pb and on diffraction in pp collisions are mentioned.