A study of the spin dependence of pion electroproduction near the [delta] region

Abstract

This work studies two double polarized pion electroproduction reactions 1(e', e'p)o0 and H(e', e'r+)n near the A region at the MIT-Bates Linear Accelerator Center. With the Bates Large Acceptance Spectrometer Toroid (BLAST) detector package, data were collected simultaneously for both reaction channels, covering an invariant mass range of 1.1 to 1.4 GeV and a squared four momentum transfer range of 0.1 to 0.4 (GeV/c)2. By flipping the target spin direction and the electron beam helicity, the single- (beam only and target only) and double-spin (beam-target) asymmetries were constructed from the measured yields with different spin combinations, covering two kinematic setups: longitudinal and transverse target spin orientations (with respect to the three momentum transfer direction). With a non-zero target spin angle (with respect to the beam direction), this experiment reports for the first time the full angular dependence of asymmetries, compared with theoretical predictions by several pion production models. In some kinematic bins, signs of preference of data to a specific model have been seen, and hints of systematic deviation of data from models have also been observed. Thus, the necessity of new constraints to the pion production models is indicated by this work.