Measurement of the parity-violating longitudinal single-spin asymmetry for $W^{\pm}$ boson production in polarized proton-proton collisions at $\sqrt{s} = 500 $GeV

TL;DR

This paper reports the first measurement of parity-violating single-spin asymmetries in W boson production in polarized proton-proton collisions at 500 GeV, providing insights into polarized quark distributions.

Contribution

It presents the first experimental measurement of asymmetries for W boson production at RHIC, testing predictions based on polarized quark and antiquark distributions.

Findings

Measured asymmetries are consistent with theoretical predictions.

Results support existing models of polarized quark distributions.

Asymmetries have opposite signs for W+ and W- bosons.

Abstract

We report the first measurement of the parity violating single-spin asymmetries for midrapidity decay positrons and electrons from $W^{+}$ and $W^{-}$ boson production in longitudinally polarized proton-proton collisions at $\sqrt{s}=500 $GeV by the STAR experiment at RHIC. The measured asymmetries, $A^{W^+}_{L}=-0.27\pm 0.10\;({\rm stat.})\pm 0.02\;({\rm syst.}) \pm 0.03\;({\rm norm.})$ and $A^{W^-}_{L}=0.14\pm 0.19\;({\rm stat.})\pm 0.02 \;({\rm syst.})\pm 0.01\;({\rm norm.})$, are consistent with theory predictions, which are large and of opposite sign. These predictions are based on polarized quark and antiquark distribution functions constrained by polarized DIS measurements.