# Azimuthal asymmetries in unpolarized SIDIS and Drell-Yan processes: a case study towards TMD factorization at subleading twist

## TL;DR

This paper investigates azimuthal asymmetries in unpolarized SIDIS and Drell-Yan processes, proposing a factorized expression for the $ ext{cos}\, ext{phi}$ modulation at low transverse momentum, advancing TMD factorization at subleading twist.

## Contribution

It introduces a new factorized formula for azimuthal asymmetries that extends TMD factorization to subleading twist, bridging low and high transverse momentum regimes.

## Key findings

- Proposes a tree-level based factorized expression for azimuthal asymmetries.
- Conjectures the formula's validity within TMD factorization at subleading twist.
- Matches collinear factorization results at high transverse momentum.

## Abstract

We consider the azimuthal distribution of the final observed hadron in semi-inclusive deep-inelastic scattering and the lepton pair in the Drell-Yan process. In particular, we focus on the $\cos \phi$ modulation of the unpolarized cross section and on its dependence upon transverse momentum. At low transverse momentum, for these observables we propose a factorized expression based on tree-level approach and conjecture that the same formula is valid in transverse-momentum dependent (TMD) factorization when written in terms of subtracted TMD parton distributions. Our formula correctly matches with the collinear factorization results at high transverse momentum, solves a long-standing problem and is a necessary step towards the extension of the TMD factorization theorems up to the subleading twist.