Polarization in Hyperon Photo- and Electro- Production

TL;DR

This paper discusses polarization measurements in hyperon photoproduction, focusing on the reaction gamma + p -> K+ + Lambda, and presents empirical constraints, models, and interpretations of polarization phenomena.

Contribution

It introduces recent polarization measurements and a simplified spin-flip model, providing new empirical constraints and semi-classical insights into hyperon polarization mechanisms.

Findings

Empirical constraints on helicity amplitudes for gamma + p -> K+ + Lambda.

A simplified spin-flip and non-flip amplitude model.

A semi-classical explanation of polarization emergence.

Abstract

Multiple polarization observables must be measured to access the amplitude structure of pseudoscalar meson photoproduction off the proton. The hyperon-producing reactions are especially attractive to study, since the weak decays allow straightforward measurement of the induced and recoil polarization observables. In this paper we emphasize $\gamma + p \to K^+ + \Lambda$, discussing recent measurements of $C_x$, $C_z$, and $P$ for this reaction. An empirical constraint on the helicity amplitudes is obtained. A simplified model involving spin-flip and spin non-flip amplitudes is presented. Finally, a semi-classical model of how the polarization may arise is presented.