Measurement of azimuthal asymmetries in SIDIS on unpolarized protons

The COMPASS Collaboration is measuring the asymmetries in the azimuthal distributions of positive and negative hadrons produced in Deep Inelastic Scattering (DIS) on unpolarized protons. The data have been collected in 2016 and 2017 with a 160 GeV/c muon beam scattering off a liquid hydrogen target. The amplitudes of three modulations, AcosϕhUU, Acos2ϕhUU and AsinϕhLU are measured as function of the Bjorken variable x, of the fraction of virtual photon energy carried by the hadron z, and of the hadron transverse momentum with respect to the virtual photon phT. The relevance of azimuthal asymmetries lies in the possibility to get information on the intrinsic transverse momentum of the quark as well as on the still unknown Boer-Mulders parton distribution function. The preliminary results from 2016 data shown here confirm the strong kinematic dependencies observed in previous measurements conducted by COMPASS, HERMES and CLAS.