Beam-target double-spin asymmetries and target single-spin asymmetries were measured for the exclusive π0 electroproduction reaction γp0, expanding an analysis of the γp+ 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.

Document Type


Publication Date


Notes/Citation Information

Published in Physical Review C, v. 95, issue 3, 035207, p. 1-12.

©2017 American Physical Society

The copyright holder has granted permission for posting the article here.

Due to the large number of authors, only the first 30 and the authors affiliated with the University of Kentucky are listed in the author section above. For the complete list of authors, please download this article or visit: https://doi.org/10.1103/PhysRevC.95.035207

This group of authors is collectively known as the CLAS Collaboration.

Digital Object Identifier (DOI)


exclpi0.txt (346 kB)
Supplemental Material

Included in

Nuclear Commons