Gluon Sivers function from forward exclusive ${\chi }_{c1}$ photoproduction on unpolarized protons

Sanjin Benic, Adrian Dumitru, Leszek Motyka +1

Exclusive production of a ${\chi }_{c1}$ axial vector quarkonia in photon-proton scattering at high energies requires a $C$-odd $t$-channel exchange. In the limit of vanishing momentum t…