# Feasibility Studies for Single Transverse-Spin Asymmetry Measurements at a Fixed-Target Experiment Using the LHC Proton and Lead Beams (AFTER@LHC)

## TL;DR

This paper explores the potential of the AFTER@LHC fixed-target experiment to measure single transverse-spin asymmetries in quarkonium and Drell-Yan processes, aiming to deepen understanding of proton spin structure.

## Contribution

It presents sensitivity studies demonstrating the feasibility of measuring $A_N$ for various particles using LHC beams and specific detectors, highlighting the experiment's unique kinematic coverage and luminosity.

## Key findings

- Feasibility of measuring $A_N$ for $J/\psi$, $\Upsilon$, and Drell-Yan processes.
- Potential to gain new insights into transverse-momentum-dependent PDFs.
- Complementary to existing collider experiments like RHIC.

## Abstract

The measurement of Single Transverse-Spin Asymmetries, $A_N$, for various quarkonium states and Drell-Yan lepton pairs can shed light on the orbital angular momentum of quarks and gluons, a fundamental ingredient of the proton-spin puzzle. The AFTER@LHC proposal combines a unique kinematic coverage and large luminosities thanks to the Large Hadron Collider beams to deliver precise measurements, complementary to the knowledge provided by collider experiments such as at RHIC. In this paper, we report on sensitivity studies for $J/\psi$, $\Upsilon$ and Drell-Yan $A_N$ done using the performance of LHCb-like or ALICE-like detectors, combined with polarised gaseous hydrogen and helium-3 targets. In particular, such analyses will provide us with new insights and knowledge about transverse-momentum-dependent parton distribution functions for quarks and gluons and on twist-3 collinear matrix elements in the proton and the neutron.