Relative Spin Polarization of Parity-Violating Asymmetries

TL;DR

This paper introduces a new concept of relative spin polarization to better interpret parity-violating asymmetries in polarized electron scattering, emphasizing the dependence on spin orientation and relative velocity.

Contribution

It provides exact calculations of parity-violating asymmetries using spin projection operators and proposes the concept of relative spin polarization for interpretation.

Findings

Parity-violating factor depends on spin polarization and relative velocity.

Sign of the parity-violating factor varies with spin orientation.

New interpretation of asymmetries based on relative spin polarization.

Abstract

Parity-violating asymmetries in polarized electron scattering have been interpreted as the asymmetries between opposite helicities of incoming fermion based on the approximation of the spin polarization operator. Here exact calculations of cross sections for parity-violating asymmetries in SLAC E158 and SLD have been performed using spin projection operators. And the parity-violating factor incorporating with spin polarization and momentum has been identified and shown that its sign depends on the spin polarization of incoming particle and the relative velocity of incoming and target particles. Therefore, I suggest a new concept of relative spin polarization to interpret the parity-violating asymmetry as contributed by the antisymmetric nature of the weak interactions depending on whether the spin direction of the incoming electron is inward or outward relative to the target electron.