We report the first observation of the parity-violating gamma-ray asymmetry A np γ in neutronproton capture using polarized cold neutrons incident on a liquid parahydrogen target at the Spallation Neutron Source at Oak Ridge National Laboratory. A np γ isolates the ∆I = 1, 3 S1 → 3 P1 component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory. We measured A np γ = (−3.0 ± 1.4(stat.) ± 0.2(sys.)) × 10 −8 , which implies a DDH weak πN N coupling of h 1 π = (2.6 ± 1.2(stat.) ± 0.2(sys.)) × 10 −7 and a pionless EFT constant of C 3 S 1 → 3 P 1 /C0 = (−7.4 ± 3.5(stat.) ± 0.5(sys.)) × 10 −11 MeV −1 . We describe the experiment, data analysis, systematic uncertainties, and implications of the result.
Chemiresistors (conductometric sensor) were fabricated on the basis of novel nanomaterials—silica nanosprings ALD coated with ZnO. The effects of high temperature and UV illumination on the electronic and gas sensing properties of chemiresistors are reported. For the thermally activated chemiresistors, a discrimination mechanism was developed and an integrated sensor-array for simultaneous real-time resistance scans was built. The integrated sensor response was tested using linear discriminant analysis (LDA). The distinguished electronic signatures of various chemical vapors were obtained at ppm level. It was found that the recovery rate at high temperature drastically increases upon UV illumination. The feasibility study of the activation method by UV illumination at room temperature was conducted.
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