Speaker
Description
Among the 8 leading-twist independent transverse momentum dependent fragmentation functions (TMD-FFs), the Collins function is the one describing the production of unpolarized hadrons from transversely polarized quarks. This FF is usually extracted, together with the TMD transversity distribution, from global fits to semi-inclusive DIS and $e^+e^-$ annihilation into hadron pairs data. Other notable probes are the azimuthal asymmetries for pion-in-jet production in polarized $pp$ collisions.
In this talk, we propose to study the Collins effect in new and complementary processes, the production of two almost back to back hadrons in $\gamma\gamma$ collisions in $e^+e^-$ and heavy nuclei scattering processes. At variance with $e^+e^- \to h_1 h_2 X$, these processes present advantages on both theorethical and experimental sides: a different weighting of the quark charges ($e_q^4$ vs $e_q^2$) and a wide range of $\gamma\gamma$ luminosity respectively. Adopting two different Collins FF extractions, we present predictions for future high luminosity experiments, such as FCC-ee or PbPb collisions for the High-Luminosity phase of the LHC.