Analysis of the cos(2φ) modulation in semi-inclusive deep-inelastic scattering*

The 3D momentum-space tomography of hadrons can be studied through azimuthal modulations that arise in the cross-section of high-energy lepton-nucleon semi-inclusive deep-inelastic scattering (SIDIS).  These collisions are sensitive to parton intrinsic transverse momentum kT. The cos(2φ) modulation has two sources: a correlation between parton transverse spin and kT, encoded in the twist-2 Boer-Mulders Transverse Momentum Dependent (TMD) function, and a higher-twist (twist-4) so-called Cahn effect involving unpolarized TMD functions.  In this work, we study SIDIS data from the HERMES, COMPASS, and CLAS collaborations in order to extract the Boer-Mulders function while considering contributions from the Cahn effect. To properly fit data from all collaborations, TMD evolution was implemented to account for how the TMDs change with the resolution scale Q2. Also, model calculations show that the Boer-Mulders TMD function is proportional to the Sivers TMD function, and we explore the validity of this relation given current data.