Target and beam-target spin asymmetries in exclusive π+ and π– electroproduction with 1.6- to 5.7-GeV electrons

Here, beam-target double-spin asymmetries and target single-spin asymmetries in exclusive π⁺ and quasiexclusive π^– electroproduction were obtained from scattering of 1.6- to 5.7-GeV longitudinally polarized electrons from longitudinally polarized protons (for π⁺) and deuterons (for π^–) using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. The kinematic range covered is 1.1 < W < 2.6 GeV and 0.05 < Q² < 5GeV², with good angular coverage in the forward hemisphere. The asymmetry results were divided into approximately 40 000 kinematic bins for π⁺ from free protons and 15 000 bins for π^– production from bound nucleons in the deuteron. The present results are found to be in reasonable agreement with fits to previous world data for W < 1.7 GeV and Q² < 0.5GeV², with discrepancies increasing at higher values of Q², especially for W > 1.5 GeV. Very large target-spin asymmetries are observed for W > 1.6 GeV. When combined with cross-section measurements, the present results can provide powerful constraints on nucleon resonance amplitudes at moderate and large values of Q², for resonances with masses as high as 2.3 GeV.