Linearly polarized gluons inside an unpolarized proton contribute to the transverse momentum distributions of (pseudo)scalar particles produced in hadronic collisions, such as Higgs bosons and quarkonia with even charge conjugation ($\eta_c$, $\eta_b$, $\chi_{ c0}$, $\chi_{ b0}$). Moreover, they can produce azimuthal asymmetries in the associated production of a photon and a $J/\psi$ or a $\Upsilon$ particle, in a kinematic configuration in which they are almost back to back. These observables, which can be measured in the running experiments at the LHC, could lead to a first extraction of both the polarized and the unpolarized gluon distributions and allow for a study of their process and energy scale dependences.
Categories: hep-ph