Speaker
Description
In recent years the STAR Collaboration collected a large sample
of ultra-peripheral heavy-ion collisions. The photoproduction of
J/$\psi$ vector mesons is sensitive to the gluon content of the target
nucleon or nucleus. We will present results from a statistically
large sample of J/$\psi$ production in Au+Au collisions. A significant
result comes from the study of the $p_T$ distributions, which clearly
show two components, from scattering off the entire Au nucleus or off
individual nucleons inside the nucleus. From a smaller sample of J/$\psi$
production in p+Au collisions, with polarized protons, we will discuss
the status of a first study of the asymmetry of J/$\psi$ production.
A non-zero asymmetry would be the first measure of the generalized
parton distribution, $E_g$, for gluons, which is connected with the
orbital angular momentum of partons in the nucleon. The present study
is a proof-of-principle, and we will discuss the possibilities with
larger data samples from future polarized p+p and p+Au RHIC runs.
