T-Odd Gluon TMDs Inside a Transversely Polarized Hadron

We consider the relevant gluon transverse momentum dependent distributions (TMDs) in the spin asymmetries generated by the scattering off transversely polarized hadrons. At large transverse momentum they can be expressed in terms of different collinear distributions, via perturbatively calculable Wilson coefficients. We calculate these coefficients at next-to-leading order, and show that when the small-x limit is taken only one independent function remains for dipole-type gluon TMDs: the so-called spin-dependent odderon. This universal origin for the spin asymmetries is of importance to better understand hadron substructure.