# Measurement of the longitudinal spin asymmetries for weak boson production in proton-proton collisions at $\sqrt{s}$ = 510 GeV

## TL;DR

This paper presents new measurements of spin asymmetries in W and Z boson production in polarized proton collisions at 510 GeV, providing insights into quark helicity distributions and comparing results with theoretical models.

## Contribution

It reports novel measurements of single and double-spin asymmetries in W and Z boson production, enhancing understanding of quark helicity distributions in protons.

## Key findings

- Evidence for differences between nd ar quark helicity distributions.
- Consistent results with previous measurements and theoretical expectations.
- New constraints on polarized parton distribution functions.

## Abstract

We report new STAR measurements of the single-spin asymmetries $A_L$ for $W^+$ and $W^-$ bosons produced in polarized proton--proton collisions at $\sqrt{s}$ = 510 GeV as a function of the decay-positron and decay-electron pseudorapidity. The data were obtained in 2013 and correspond to an integrated luminosity of 250 pb$^{-1}$. The results are combined with previous results obtained with 86 pb$^{-1}$. A comparison with theoretical expectations based on polarized lepton-nucleon deep-inelastic scattering and prior polarized proton--proton data suggests a difference between the $\bar{u}$ and $\bar{d}$ quark helicity distributions for $0.05 < x < 0.25$. In addition, we report new results for the double-spin asymmetries $A_{LL}$ for $W^\pm$, as well as $A_L$ for $Z/\gamma^*$ production and subsequent decay into electron--positron pairs.