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 Δ0 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.
Weather Research and Forecasting (WRF) single-column model simulations were performed in the late summer of 2012 in order to analyse the diurnal changes of the planetary boundary layer (PBL). Five ...PBL schemes were tested with the WRF. From the radiometer and wind-profiler measurements at one station, derived PBL heights were also compared to the simulations. The weather conditions during the measurement period proved to be dry; the soil moisture was below wilting point 85 percent of the time. Results show that (1) simulation-based PBL heights are overestimated by about 500-1000 m with respect to the observation-based PBL heights, and (2) PBL height deviations between different observation-based methods (around 700 m in the midday) are comparable with PBL height deviations between different model schemes used in the WRF single-column model. The causes of the deviations are also discussed. It is shown that in the estimation of the PBL height the relevance of the atmospheric profiles could be as important as the relevance of the estimation principles.
The effects of soil hydraulic parameter and stomatal functioning parameterization changes upon the precipitation fields of storms were compared and analyzed. The analysis was performed using results ...from the Penn State-NCAR MM5 Modeling System. Two sets of soil hydraulic parameters, from the USA and Hungary, were used. Stomatal functioning is parameterized as simply as possible using Jarvis' approach. The days chosen for analysis (18th April 2005 and 7th August 2006) seemed to be favourable for local storms to form when the land-surface/air interaction is the strongest. Both days were wet, however, the prevailing moisture was somewhat larger on 18th April 2005.
Precipitation fields were statistically analyzed in details. First, the simulated and observed fields were compared. The observed fields were estimated from rain-gauge data applying the ordinary block kriging interpolation technique. The agreement between the simulated and observed fields was estimated using categorical and continuous verification indices. Significance tests were done to estimate how large the obtained differences were.
The results obtained indicate that precipitation fields are at least as sensitive to changes in soil hydraulic parameters as to changes in stomatal functioning parameterization. The simple Student t-test hypothesis was applied to estimate how large the precipitation differences obtained were. According to the estimates, the TSS differences obtained by soil parameter and stomatal functioning parameterization changes are significant on the 10% level. The acquired differences do not depend on the initialization of soil moisture.
The results suggest that all weather and climate models used for regional purposes should prefer local soil data instead of some common globally used soil datasets. This is at least as important as the parameterization of stomatal functioning.
As part of an experiment to measure the spectrum of photons emitted in beta-decay of the free neutron, we developed and operated a detector consisting of 12 bismuth germanate (BGO) crystals coupled ...to avalanche photodiodes (APDs). The detector was operated near liquid nitrogen temperature in the bore of a superconducting magnet and registered photons with energies from 5keV to 1000keV. To enlarge the detection range, we also directly detected soft X-rays with energies between 0.2keV and 20keV with three large area APDs. The construction and operation of the detector are presented, as well as information on operation of APDs at cryogenic temperatures.
The violation of mirror symmetry in the weak force provides a powerful tool to study the internal structure of the proton. Experimental results have been obtained that address the role of strange ...quarks in generating nuclear magnetism. The measurement reported here provides an unambiguous constraint on strange quark contributions to the proton's magnetic moment through the electron-proton weak interaction. We also report evidence for the existence of a parity-violating electromagnetic effect known as the anapole moment of the proton. The proton's anapole moment is not yet well understood theoretically, but it could have important implications for precision weak interaction studies in atomic systems such as cesium.
Tensor polarization observables ( t(20), t(21), and t(22)) have been measured in elastic electron-deuteron scattering for six values of momentum transfer between 0.66 and 1.7 (GeV/c)(2). The ...experiment was performed at the Jefferson Laboratory in Hall C using the electron High Momentum Spectrometer, a specially designed deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new data determine to much larger Q2 the deuteron charge form factors G(C) and G(Q). They are in good agreement with relativistic calculations and disagree with perturbative QCD predictions.
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