Speaker
Description
We study transverse Single-Spin Asymmetries (SSAs) for $J/\psi$ production in $p^↑ p→J/\psi+X$ within the phenomenological approaches of the Generalized Parton Model (GPM) and its extension, the Colour Gauge Invariant-GPM (CGI-GPM). Such SSAs are expected to give access to the so-called gluon Sivers function (GSF), a still poorly known transverse momentum dependent distribution (TMD). In both schemes, transverse momentum and spin effects are taken into account in the calculation of the asymmetries but, while in the GPM TMDs are considered to be universal, in the CGI-GPM the GSF becomes process dependent because of the additional inclusion of initial- and final-state interactions. Concerning quarkonium formation, we adopt both the Colour-Singlet Model (CSM) and the Non-Relativistic QCD (NRQCD) approach. We compare the results obtained by maximizing the GSF in the different frameworks with existing data from the PHENIX Collaboration at RHIC. Moreover, we provide corresponding estimates for future fixed-target experiments at the LHC.
