31st International Workshop on Deep Inelastic Scattering

Energy dependence of coherent J/ψ production off lead with ALICE

Non programmé

20m

Maison MINATEC, Grenoble, FRANCE

Regular parallel talk WG2: Small-x, Diffraction and Vector Mesons

Orateur

Guillermo Contreras (Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague, Czech Republic)

Description

ALICE has measured the diffractive photo-nuclear cross section for coherent J$/\psi$ production off lead (Pb) nuclei. This process is highly sensitive to the gluon distribution in Pb. This measurement reaches centre-of-mass energies of the photon-nucleus system up to 813 GeV which is more than 340 GeV larger than ever before. It also covers three orders of magnitude of the relevant variable, Bjorken-$x$, with cross sections measured from $x\sim {10}^{-2}$ to $x\sim {10}^{-5}$.
This unprecedented coverage allows for probing the gluonic structure of the Pb nuclei at the lowest Bjorken-$x$ possible with any current experiment, challenging both gluon saturation and shadowing models to describe the data.