# Nuclear dependence of the transverse single-spin asymmetry in the production of charged hadrons at forward rapidity in polarized $p+p$, $p+$Al, and $p+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV

## TL;DR

This study investigates how the transverse single-spin asymmetry (TSSA) in charged hadron production varies across different nuclear targets in polarized proton collisions, revealing a nuclear dependence that informs understanding of TSSAs in small systems.

## Contribution

It provides the first detailed measurement of nuclear dependence of TSSAs in charged hadron production at forward rapidity in polarized proton-nucleus collisions.

## Key findings

- Positive asymmetry in p+p collisions
- Reduced asymmetry in p+Al and p+Au collisions
- Nuclear dependence observed in TSSA measurements

## Abstract

We report on the nuclear dependence of transverse single-spin asymmetries (TSSAs) in the production of positively-charged hadrons in polarized $p^{\uparrow}+p$, $p^{\uparrow}+$Al and $p^{\uparrow}+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV. The measurements have been performed at forward rapidity ($1.4<\eta<2.4$) over the range of $1.8<p_{T}<7.0$ GeV$/c$ and $0.1<x_{F}<0.2$. We observed a positive asymmetry $A_{N}$ for positively-charged hadrons in \polpp collisions, and a significantly reduced asymmetry in $p^{\uparrow}$+$A$ collisions. These results reveal a nuclear dependence of charged hadron $A_N$ in a regime where perturbative techniques are relevant. These results provide new opportunities to use \polpA collisions as a tool to investigate the rich phenomena behind TSSAs in hadronic collisions and to use TSSA as a new handle in studying small-system collisions.