Measurement of Longitudinal Spin Asymmetries From $W\rightarrow e$ Boson Decay in Polarized pp Collisions at $\sqrt{s}=500$ GeV at RHIC-PHENIX

TL;DR

This paper reports the first measurement of parity-violating single spin asymmetries from W boson decays in polarized proton-proton collisions at 500 GeV, providing insights into the proton's spin structure.

Contribution

It presents the first observation of W production in polarized p+p collisions and measures its spin asymmetry, advancing understanding of proton spin decomposition.

Findings

W boson production confirmed in p+p collisions

Measured spin asymmetries consistent with theoretical expectations

Provides new data for quark flavor decomposition of proton spin

Abstract

We report the measurement of the parity violating single spin asymmetries for inclusive high transverse momentum electrons and positrons in polarized $p+p$ collisions at a center of mass energy of $\sqrt{s}=500$ GeV with the PHENIX detector at RHIC. These electrons are attributed to the decay of $W^\pm$ and $Z^0$ bosons, and measured production cross section is consistent with the expectations. The $W$ production is confirmed for the first time in $p+p$ collisions. Its spin asymmetry in the polarized $p+p$ collisions is a important probe for the quark flavor decomposition of the proton spin.