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Published March 20, 2012 | Published
Journal Article Open

Measurement of the Parity-Violating Asymmetry in Inclusive Electroproduction of π- near the Δ0 Resonance


The parity-violating (PV) asymmetry of inclusive π- production in electron scattering from a liquid deuterium target was measured at backward angles. The measurement was conducted as a part of the G0 experiment, at a beam energy of 360 MeV. The physics process dominating pion production for these kinematics is quasifree photoproduction off the neutron via the Δ^0 resonance. In the context of heavy-baryon chiral perturbation theory, this asymmetry is related to a low-energy constant d_Δ^- that characterizes the parity-violating γNΔ coupling. Zhu et al. calculated d_Δ^- in a model benchmarked by the large asymmetries seen in hyperon weak radiative decays, and predicted potentially large asymmetries for this process, ranging from A_γ^-=-5.2 to +5.2  ppm. The measurement performed in this work leads to A_γ^-=-0.36±1.06±0.37±0.03  ppm (where sources of statistical, systematic and theoretical uncertainties are included), which would disfavor enchancements considered by Zhu et al. proportional to V_(ud)/V_(us). The measurement is part of a program of inelastic scattering measurements that were conducted by the G0 experiment, seeking to determine the N-Δ axial transition form factors using PV electron scattering.

Additional Information

© 2012 American Physical Society. Received 7 December 2011; published 20 March 2012. We gratefully acknowledge the strong technical contributions to this experiment from many groups: Caltech, Illinois, LPSC-Grenoble, IPN-Orsay, TRIUMF and particularly the Accelerator and Hall C groups at Jefferson Lab. CNRS (France), DOE (U.S.), NSERC (Canada) and NSF (U.S.) supported this work in part.

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