Polarization of Hyperons in Elementary Photoproduction

Abstract

Recent measurements using the CLAS detector at Jefferson Lab of the reactions $\vec\gamma + p \to K^+ + \vec\Lambda$ and $\vec\gamma + p \to K^+ + \vec\Sigma^0$ have been used to extract the spin transfer coefficients $C_x$ and $C_z$ for the first time. These observables quantify the degree of the photon circular polarization that is transferred to the recoiling hyperons in the scattering plane. The unexpected result is that $\Lambda$ hyperons are produced ``100% polarized'' as seen when combining $C_x$ and $C_z$ with the induced transverse polarization, $P$. Furthermore, $C_x$ and $C_z$ seem to be linearly related. This paper discusses the experimental results and offers a hypothesis which can explain these observations. We show how the produced strange quark can be subject to a pure spin-orbit type of interaction which preserves its state of polarization throughout the hadronization process.