# Measurement of azimuthal asymmetries in SIDIS on unpolarized protons

## TL;DR

This paper reports measurements of azimuthal asymmetries in semi-inclusive deep inelastic scattering on unpolarized protons, providing insights into quark transverse momentum and Boer-Mulders functions, with results confirming previous kinematic dependencies.

## Contribution

First measurement of azimuthal asymmetries in SIDIS on unpolarized protons using COMPASS data, advancing understanding of transverse quark momentum and parton distributions.

## Key findings

- Confirmed strong kinematic dependencies of asymmetries
- Measured amplitudes of three azimuthal modulations
- Data consistent with previous experiments

## Abstract

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, $A_{UU}^{\cos\phi_h}$, $A_{UU}^{\cos 2\phi_h}$ and $A_{LU}^{\sin\phi_h}$ 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 $p_{T}^{h}$. 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.