Observation of W decay in 500 GeV p+p collisions at RHIC

TL;DR

This paper reports the first observation of W boson production in 500 GeV proton-proton collisions at RHIC, measuring the single longitudinal spin asymmetry to test polarized parton distribution models.

Contribution

It provides experimental evidence of W production at RHIC energies and measures the spin asymmetry, contributing to understanding proton spin structure.

Findings

W boson production observed at 500 GeV

Measured asymmetry $A_L$ is -0.83 with uncertainties

Results agree with polarized parton distribution function calculations

Abstract

W boson production is observed in $\sqrt{s}=500$ GeV proton proton collisions at RHIC-PHENIX experiment. The single longitudinal spin asymmetry $A_L(\overrightarrow{p}p\rightarrow W^+X)$ is measured via decay positrons in the mid rapidity region. The asymmetry $-0.83\pm0.31\pm(11%$ scale uncertainty) is consistent with calculations from various polarized parton distribution functions.