# First Measurement of Beam-Recoil Observables $C_x$ and $C_z$ in Hyperon Photoproduction

Abstract : Spin transfer from circularly polarized real photons to recoiling hyperons has been measured for the reactions $\vec\gamma + p \to K^+ + \vec\Lambda$ and $\vec\gamma + p \to K^+ + \vec\Sigma^0$. The data were obtained using the CLAS detector at Jefferson Lab for center-of-mass energies $W$ between 1.6 and 2.53 GeV, and for $-0.85<\cos\theta_{K^+}^{c.m.}< +0.95$. For the $\Lambda$, the polarization transfer coefficient along the photon momentum axis, $C_z$, was found to be near unity for a wide range of energy and kaon production angles. The associated transverse polarization coefficient, $C_x$, is smaller than $C_z$ by a roughly constant difference of unity. Most significantly, the {\it total} $\Lambda$ polarization vector, including the induced polarization $P$, has magnitude consistent with unity at all measured energies and production angles when the beam is fully polarized. For the $\Sigma^0$ this simple phenomenology does not hold. All existing hadrodynamic models are in poor agreement with these results.
Document type :
Journal articles

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Contributor : Dominique Girod <>
Submitted on : Wednesday, May 16, 2007 - 3:28:33 PM
Last modification on : Wednesday, April 21, 2021 - 8:36:02 AM

### Citation

R.K. Bradford, R.A. Schumacher, G. Adams, M.J. Amaryan, P. Ambrozewicz, et al.. First Measurement of Beam-Recoil Observables $C_x$ and $C_z$ in Hyperon Photoproduction. Physical Review C, American Physical Society, 2007, 75, pp.035205. ⟨10.1103/PhysRevC.75.035205⟩. ⟨in2p3-00147310⟩

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