Recoil Polarization and Beam-Recoil Double Polarization Measurement of η Electroproduction on the Proton in the Region of the S_(11)(1535) Resonance

摘要

The beam-recoil double polarization P_(x~1)~h and P_(z~1)~h and the recoil polarization P_(y~1) were measured for the first time for the p(e, e'p)η reaction at a four-momentum transfer of Q~2 =0.1 GeV~2/c~2 and a center of mass production angle of θ = 120° at the Mainz Microtron MAMI-C. With a center of mass energy range of 1500 MeV < W < 1550 MeV the region of the 5_(11)(1535) and D_(13)(1520) resonance was covered. The results are discussed in the framework of a phenomenological isobar model (Eta-MAID). While _(x~1)h, and P_(z~1)h, are in good agreement with the model, P_(y~1) shows a significant deviation, consistent with existing photoproduction data on the polarized-target asymmetry.