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Register a new userMeasurement of Parity-Violating Asymmetry in Electron-Deuteron Inelastic Scattering
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The parity-violating asymmetries between a longitudinally-polarized electron beam and an unpolarized deuterium target have been measured recently. The measurement covered two kinematic points in the deep inelastic scattering region and five in the nucleon resonance region. We provide here details of the experimental setup, data analysis, and results on all asymmetry measurements including parity-violating electron asymmetries and those of inclusive pion production and beam-normal asymmetries. The parity-violating deep-inelastic asymmetries were used to extract the electron-quark weak effective couplings, and the resonance asymmetries provided the first evidence for quark-hadron duality in electroweak observables. These electron asymmetries and their interpretation were published earlier, but are presented here in more detail.
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We report on parity-violating asymmetries in the nucleon resonance region measured using $5 - 6$ GeV longitudinally polarized electrons scattering off an unpolarized deuterium target. These results are the first parity-violating asymmetry data in the resonance region beyond the $Delta(1232)$, and provide a verification of quark-hadron duality in the nucleon electroweak $gamma Z$ interference structure functions at the (10-15)% level. The results are of particular interest to models relevant for calculating the $gamma Z$ box-diagram corrections to elastic parity-violating electron scattering measurements.
We analyze the parity-violating (PV) components of the analyzing power in elastic electron-proton scattering and discuss their sensitivity to the strange quark contributions to the proton weak form factors. We point out that the component of the analyzing power along the momentum transfer is independent of the electric weak form factor and thus compares favorably with the PV beam asymmetry for a determination of the strangeness magnetic moment. We also show that the transverse component could be used for constraining the strangeness radius. Finally, we argue that a measurement of both components could give experimental information on the strangeness axial charge.
We report the measurement of the parity-violating asymmetry for the inelastic scattering of electrons from the proton, at $Q^2 = 0.082$ GeV$^2$ and $ W = 2.23$ GeV, above the resonance region. The result $A_{rm Inel} = - 13.5 pm 2.0 ({rm stat}) pm 3.9 ({rm syst})$~ppm agrees with theoretical calculations, and helps to validate the modeling of the $gamma Z$ interference structure functions $F_1^{gamma Z}$ and $F_2^{gamma Z}$ used in those calculations, which are also used for determination of the two-boson exchange box diagram ($Box_{gamma Z}$) contribution to parity-violating elastic scattering measurements. A positive parity-violating asymmetry for inclusive $pi^-$ production was observed, as well as positive beam-normal single-spin asymmetry for scattered electrons and a negative beam-normal single-spin asymmetry for inclusive $pi^-$ production.
We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from protons. Significant contributions to this asymmetry could arise from the contributions of strange form factors in the nucleon. The measured asymmetry is $A = -15.05 pm 0.98 ({rm stat}) pm 0.56 ({rm syst})$ ppm at the kinematic point $<theta_{rm lab} > = 12.{3^circ} $ and $<Q^2 > = 0.477$ (GeV/c)$^2$. Based on these data as well as data on electromagnetic form factors, we extract the linear combination of strange form factors $G^s_E + 0.392 G^s_M = 0.014 pm 0.020 pm 0.010$ where the first error arises from this experiment and the second arises from the electromagnetic form factor data. This paper provides a full description of the special experimental techniques employed for precisely measuring the small asymmetry, including the first use of a strained GaAs crystal and a laser-Compton polarimeter in a fixed target parity-violation experiment.
We report on a measurement of the tensor-analyzing power T20 in elastic electron-deuteron scattering in the range of four-momentum transfer from 1.8 to 3.2 fm-1. Electrons of 704 MeV were scattered from a polarized deuterium internal target. The tensor polarization of the deuterium nuclei was determined with an ion-extraction system, allowing an absolute measurement of T20. The data are described well by a non-relativistic calculation that includes the effects of meson-exchange currents.
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