Nonperturbative functions for SIDIS and Drell–Yan processes

We update the well-known BLNY fit to the low transverse momentum Drell–Yan lepton pair productions in hadronic collisions, by considering the constraints from the semi-inclusive hadron production in deep inelastic scattering (SIDIS) from HERMES and COMPASS experiments. We follow the Collins–Soper–Sterman (CSS) formalism with the [Formula: see text]-prescription. A nonperturbative form factor associated with the transverse momentum dependent quark distributions is found in the analysis with a new functional form different from that of BLNY. This releases the tension between the BLNY fit to the Drell–Yan data with the SIDIS data from HERMES/COMPASS in the CSS resummation formalism.

PHENOMENOLOGY OF THE SIVERS EFFECT WITH TMD EVOLUTION

Recently, theoretical developments have led to the QCD evolution equations for the unpolarized Transverse Momentum Dependent (TMD) distribution functions and for the Sivers function (TMD-evolution). We tested whether the proposed TMD-evolution can already be observed in the SIDIS data on the Sivers asymmetry. Although very preliminary, our analysis shows that data are compatible with such an evolution with a clear indication of evolution in the x-dependent data subsets.