Polarization of Hyperons in Elementary Photoproduction

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 determined the spin transfer coefficients $C_x$ and $C_z$ for the first time. These observables quantify 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 previously-measured induced transverse polarization, $P$. Furthermore, $C_x$ and $C_z$ seem to be linearly related. We present the experimental results and offer a hypothesis which can explain these observations: the produced strange quark, when subjected to a pure spin-orbit type of interaction, preserves its state of polarization throughout the hadronization process. This hypothesis suggests that quark dynamics are relevant to the formation of hadrons even in the ``nucleon resonance'' region of excitation.