Target and beam-target spin asymmetries in exclusive pion electroproduction for Q2>1 GeV2. II. ep→eπ0p TARGET and BEAM-TARGET SPIN .... II. ... P. E. BOSTED et al.

Beam-target double-spin asymmetries and target single-spin asymmetries were measured for the exclusive π⁰ electroproduction reaction γp → pπ⁰, expanding an analysis of the γp → nπ⁺ reaction from the same experiment. The results were obtained from scattering of 6-GeV longitudinally polarized electrons off longitudinally polarized protons using the CEBAF Large Acceptance Spectrometer at Jefferson Laboratory. The kinematic ranges covered are 1.1 < W < 3 GeV and 1 < Q² < 6 GeV². Results were obtained for about 5700 bins in W, Q², cos(θ*), and φ*. The beam-target asymmetries were found to generally be greater than zero, with relatively modest φ* dependence. The target asymmetries exhibit very strong φ* dependence, with a change in sign occurring between results at low W and high W, in contrast to π⁺ electroproduction. Reasonable agreement is found with phenomenological fits to previous data for W < 1.6 GeV, but significant differences are seen at higher W. When combined with cross-sectional measurements, as well as π⁺ observables, the present results will provide powerful constraints on nucleon resonance amplitudes at moderate and large values of Q², for resonances with masses as high as 2.4 GeV.