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Browsing by Author "Berryman, Jeffrey M."

Now showing 1 - 5 of 5
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    Future searches for light sterile neutrinos at nuclear reactors
    Berryman, Jeffrey M.; Delgadillo, Luis A.; Huber, Patrick (American Physical Society, 2022-02-02)
    We study the optimization of a green-field, two-baseline reactor experiment with respect to the sensitivity for electron antineutrino disappearance in search of a light sterile neutrino. We consider both commercial and research reactors and identify as key factors the distance of closest approach and detector energy resolution. We find that a total of 5 tons of detectors deployed at a commercial reactor with a closest approach of 25 m can probe the mixing angle sin(2) 2 theta down to similar to 5 x 10(-3) around Delta m(2) similar to 1 eV(2). The same detector mass deployed at a research reactor can be sensitive up to Delta m(2) similar to 20-30 eV(2) assuming a closest approach of 3 m and excellent energy resolution, such as that projected for the Taishan Antineutrino Observatory. We also find that lithium doping of the reactor could be effective in increasing the sensitivity for higher Delta m(2) values.
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    Reevaluating reactor antineutrino anomalies with updated flux predictions
    Berryman, Jeffrey M.; Huber, Patrick (2020-01-14)
    Hints for the existence of a sterile neutrino at nuclear reactors are reexamined using two updated predictions for the fluxes of antineutrinos produced in fissions. These new predictions diverge in their preference for the rate deficit anomaly, relative to previous analyses, but the anomaly in the ratios of measured antineutrino spectra persists. We comment on upcoming experiments and their ability to probe the preferred region of the sterile-neutrino parameter space in the electron neutrino disappearance channel.
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    Searches for decays of new particles in the DUNE Multi-Purpose near Detector
    Berryman, Jeffrey M.; de Gouvea, Andre; Fox, Patrick J.; Kayser, Boris J.; Kelly, Kevin J.; Raaf, Jennifer L. (2020-02-27)
    One proposed component of the upcoming Deep Underground Neutrino Experiment (DUNE) near detector complex is a multi-purpose, magnetized, gaseous argon time projection chamber: the Multi-Purpose Detector (MPD). We explore the new-physics potential of the MPD, focusing on scenarios in which the MPD is significantly more sensitive to new physics than a liquid argon detector, specifically searches for semi-long-lived particles that are produced in/near the beam target and decay in the MPD. The specific physics possibilities studied are searches for dark vector bosons mixing kinetically with the Standard Model hypercharge group, leptophilic vector bosons, dark scalars mixing with the Standard Model Higgs boson, and heavy neutral leptons that mix with the Standard Model neutrinos. We demonstrate that the MPD can extend existing bounds in most of these scenarios. We illustrate how the ability of the MPD to measure the momentum and charge of the final state particles leads to these bounds.
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    Statistical significance of the sterile-neutrino hypothesis in the context of reactor and gallium data
    Berryman, Jeffrey M.; Coloma, Pilar; Huber, Patrick; Schwetz, Thomas; Zhou, Albert (Springer, 2022-02-08)
    We evaluate the statistical significance of the 3+1 sterile-neutrino hypothesis using nu(e) and (nu) over bar (e) disappearance data from reactor, solar and gallium radioactive source experiments. Concerning the latter, we investigate the implications of the recent BEST results. For reactor data we focus on relative measurements independent of flux predictions. For the problem at hand, the usual chi(2)-approximation to hypothesis testing based on Wilks' theorem has been shown in the literature to be inaccurate. We therefore present results based on Monte Carlo simulations, and find that this typically reduces the significance by roughly 1 sigma with respect to the naive expectation. We find no significant indication in favor of sterile-neutrino oscillations from reactor data. On the other hand, gallium data (dominated by the BEST result) show more than 5 sigma of evidence supporting the sterile-neutrino hypothesis, favoring oscillation parameters in agreement with constraints from reactor data. This explanation is, however, in significant tension (similar to 3 sigma) with solar neutrino experiments. In order to assess the robustness of the signal for gallium experiments we present a discussion of the impact of cross-section uncertainties on the results.
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    Sterile neutrinos and the global reactor antineutrino dataset
    Berryman, Jeffrey M.; Huber, Patrick (2021-01-26)
    We present results from global fits to the available reactor antineutrino dataset, as of Fall 2019, to determine the global preference for a fourth, sterile neutrino. We have separately considered experiments that measure the integrated inverse-beta decay (IBD) rate from those that measure the energy spectrum of IBD events at one or more locations. The evidence that we infer from rate measurements varies between less than or similar to 3 sigma and negligible depending on the reactor antineutrino flux model employed. Moreover, we find that spectral ratios ostensibly imply greater than or similar to 3 sigma evidence, consistent with previous work, though these measurements are known to be plagued by issues related to statistical interpretation; these results should therefore be viewed cautiously. The software used is the newly developed GLoBESfit tool set which is based on the publicly available GLoBES framework and will be released as open-source software.