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Measurement of the Parity-Violating Asymmetry in Inclusive Electroproduction of pi(-) near the Delta(0) Resonance
Androic, D. Seva, T. Armstrong, D. S. Bailey, S. L. Capuano, C. L. Phillips, S. K. Arvieux, J.
Androic, D.
Seva, T.
Armstrong, D. S.
Bailey, S. L.
Capuano, C. L.
Phillips, S. K.
Arvieux, J.
Abstract
The parity-violating (PV) asymmetry of inclusive pi(-) 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 Delta(0) resonance. In the context of heavy-baryon chiral perturbation theory, this asymmetry is related to a low-energy constant d(Delta)(-) that characterizes the parity-violating gamma N Delta coupling. Zhu et al. calculated d(Delta)(-) 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(gamma)(-) = -5.2 to + 5.2 ppm. The measurement performed in this work leads to A(gamma)(-) = -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 - Delta axial transition form factors using PV electron scattering.
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2012-01-01
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Physics
DOI
https://doi.org/10.1103/PhysRevLett.108.122002