# Double-Longitudinal Spin Asymmetry in Single-Inclusive Lepton Scattering at NLO

## TL;DR

This paper calculates the double-spin asymmetries in lepton-nucleon scattering at NLO, compares with existing data, and emphasizes the need for further measurements at current and future experiments to improve understanding.

## Contribution

It provides NLO theoretical predictions for double-spin asymmetries in lepton scattering and compares them with experimental data, highlighting areas for further investigation.

## Key findings

- Partial agreement with SLAC E155 data
- Predictions for future experiments
- Call for more measurements to test QCD understanding

## Abstract

We calculate the double-spin asymmetries $A_{\mathrm{LL}}$ for the processes $\ell N\to h X$ and $\ell N\to {\mathrm{jet}}\, X$ at next-to-leading order accuracy in perturbative QCD. We compare our theoretical results for $A_{\mathrm{LL}}$ to data from the SLAC E155 experiment, finding only partially satisfactory agreement. We conclude that measurements of $A_{\mathrm{LL}}$ and the relevant polarized and unpolarized cross sections should be performed at the present-day fixed-target lepton scattering experiments, as well as at a future electron ion collider, in order to verify our understanding of this process. We present predictions of the longitudinal double-spin asymmetries for these experiments.