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E89-004

Spokesperson
R. A. Schumacher
Year
2005
Abstract
Spin transfer from circularly polarized real photons to recoiling hyperons has been measured for the reactions gamma + p -> K^+ + 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 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.
Comment
Correlated data on W & cos(theta) distribution are available in E19M33 and E19M34 measurements.
Publication
  1. R. Bradford, R. A. Schumacher, and CLAS Collaboration First Measurement of Beam-Recoil Observables Cx and Cz in Hyperon Photoproduction // Submitted to Physical Review C
Quantities
Cx   Cz

Measurements

ID Quantity Beam Target Final state Q2min,
GeV2 		Q2max,
GeV2 		Wmin,
GeV 		Wmax,
GeV
E19M1 Cx γ p K+ Σ0 0.0 0.0 1.787 1.787
E19M2 Cz γ p K+ Σ0 0.0 0.0 1.787 1.787
E19M3 Cx γ p K+ Σ0 0.0 0.0 1.839 1.839
E19M4 Cz γ p K+ Σ0 0.0 0.0 1.839 1.839
E19M5 Cx γ p K+ Σ0 0.0 0.0 1.889 1.889
E19M6 Cz γ p K+ Σ0 0.0 0.0 1.889 1.889
E19M7 Cx γ p K+ Σ0 0.0 0.0 1.939 1.939
E19M8 Cz γ p K+ Σ0 0.0 0.0 1.939 1.939
E19M9 Cx γ p K+ Σ0 0.0 0.0 1.987 1.987
E19M10 Cz γ p K+ Σ0 0.0 0.0 1.987 1.987
E19M11 Cx γ p K+ Σ0 0.0 0.0 2.035 2.035
E19M12 Cz γ p K+ Σ0 0.0 0.0 2.035 2.035
E19M13 Cx γ p K+ Σ0 0.0 0.0 2.081 2.081
E19M14 Cz γ p K+ Σ0 0.0 0.0 2.081 2.081
E19M15 Cx γ p K+ Σ0 0.0 0.0 2.126 2.126
E19M16 Cz γ p K+ Σ0 0.0 0.0 2.126 2.126
E19M17 Cx γ p K+ Σ0 0.0 0.0 2.17 2.17
E19M18 Cz γ p K+ Σ0 0.0 0.0 2.17 2.17
E19M19 Cx γ p K+ Σ0 0.0 0.0 2.212 2.212
E19M20 Cz γ p K+ Σ0 0.0 0.0 2.212 2.212
E19M21 Cx γ p K+ Σ0 0.0 0.0 2.255 2.255
E19M22 Cz γ p K+ Σ0 0.0 0.0 2.255 2.255
E19M23 Cx γ p K+ Σ0 0.0 0.0 2.296 2.296
E19M24 Cz γ p K+ Σ0 0.0 0.0 2.296 2.296
E19M25 Cx γ p K+ Σ0 0.0 0.0 2.338 2.338
E19M26 Cz γ p K+ Σ0 0.0 0.0 2.338 2.338
E19M27 Cx γ p K+ Σ0 0.0 0.0 2.377 2.377
E19M28 Cz γ p K+ Σ0 0.0 0.0 2.377 2.377
E19M29 Cx γ p K+ Σ0 0.0 0.0 2.416 2.416
E19M30 Cz γ p K+ Σ0 0.0 0.0 2.416 2.416
E19M31 Cx γ p K+ Σ0 0.0 0.0 2.454 2.454
E19M32 Cz γ p K+ Σ0 0.0 0.0 2.454 2.454
E19M33 Cx γ p K+ Σ0 0.0 0.0 1.787 2.454
E19M34 Cz γ p K+ Σ0 0.0 0.0 1.787 2.454
Created in SINP MSU, CLAS Collaboration