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Register a new userMeasurement of Moller Scattering at 2.5 MeV
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Moller scattering is one of the most fundamental processes in QED. Understanding it to high precision is necessary for a variety of modern nuclear and particle physics experiments. In a recent calculation, existing soft-photon radiative corrections were combined with new hard-photon bremsstrahlung calculations to take into account the effect of photon emission at any photon energy, where the electron mass was included at all steps. To test the calculation, an experiment was carried out using the 3 MV Van de Graaff electrostatic accelerator at the MIT High Voltage Research Laboratory. Momentum spectra at three scattering angles at an incident electron energy of 2.5 MeV are reported here, and compared to the simulated radiative Moller spectra, based on our previous calculation. Good agreement between the measurements and our calculation is observed in the momentum spectrum at the three angles.
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Experiments searching for neutrinoless double beta decay ($0 ubetabeta$) require precise energy calibration and extremely low backgrounds. One of the most popular isotopes for $0 ubetabeta$ experiments is $^{136}$Xe. In support of these experiments, the neutron inelastic scattering properties of this isotope have been measured at the GErmanium Array for Neutron Induced Excitations (GEANIE) at the Los Alamos Neutron Science Center. Time-of-flight techniques are utilized with high-purity germanium detectors to search for inelastic scattering $gamma$ rays for neutron energies between 0.7 and 100 MeV. Limits are set on production of yet-unobserved $gamma$ rays in the energy range critical for $0 ubetabeta$ studies, and measurements are made of multiple $gamma$-ray production cross sections. In particular, we have measured the production of the 1313 keV $gamma$ ray which comes from the transition of the first-excited to ground state of $^{136}$Xe. This neutron-induced $gamma$ line may be useful for a novel energy calibration technique, described in this paper.
Kr83m with a short lifetime is an ideal calibration source for liquid xenon or liquid argon detector. The 83mKr isomer can be generated through the decay of Rb83 isotope, and Rb83 is usually produced by proton beams bombarding natural krypton atoms. In this paper, we report a successful production of Rb83/Kr83m with 3.4 MeV proton beam energy and measure the production rate with such low proton energy for the first time. Another production attempt was performed with newly available 20 MeV proton beam in China, the production rate is consistent with our expectation. The produced Kr83m source has been successfully injected into PandaX-II liquid xenon detector and yielded enough statistics for detector calibration.
Understanding of $gamma$-ray production via neutron interactions on oxygen is essential for the study of neutrino neutral-current quasielastic interactions in water Cherenkov detectors. A measurement of $gamma$-ray production from such reactions was performed using a 77~MeV quasi-monoenergetic neutron beam. Several $gamma$-ray peaks, which are expected to come from neutron-${rm ^{16}O}$ reactions, are observed and production cross sections are measured for nine $gamma$-ray components of energies between 2 and 8~MeV. These are the first measurements at this neutron energy using a nearly monoenergitic beam.
We describe a double-scattering experiment with a novel tagged neutron beam to measure differential cross sections for np back-scattering to better than 2% absolute precision. The measurement focuses on angles and energies where the cross section magnitude and angle-dependence constrain the charged pion-nucleon coupling constant, but existing data show serious discrepancies among themselves and with energy-dependent partial wave analyses (PWA). The present results are in good accord with the PWA, but deviate systematically from other recent measurements.
The $^{18}$Ne($alpha,p$)$^{21}$Na reaction plays a significant role in Type-I X-ray bursts. It is a major path in the breakout from the hot-CNO cycles to the synthesis of heavier elements in the $alpha p$-- and $rp$-processes. An experiment to determine the cross section of this reaction was performed with the ANASEN active-target detector system, determining the cross section at energies between 2.5 and 4 MeV in the center-of-mass frame. The measured cross sections for reactions populating the ground state in $^{21}$Na are consistent with results obtained from the time-inverse reaction, but significantly lower than the previously published experimental data of direct measurements. The total cross sections are also compared with those derived from indirect methods and statistical-model calculations. This experiment establishes a new experimental data set on the excitation function of the $^{18}$Ne($alpha,p$)$^{21}$Na reaction, revealing the significance of the excited states contributions to the total reaction cross section and allowing to separate the contribution of the $(alpha,2p)$ reaction. The impact of the measured cross section on thermal reaction rates is discussed.
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