We present that the next-generation Enriched Xenon Observatory (nEXO) is a proposed experiment to search for neutrinoless double- β (0νββ) decay in 136Xe with a target half-life sensitivity of ...approximately 1028 yr using 5 × 103 kg of isotopically enriched liquid-xenon in a time projection chamber. This improvement of two orders of magnitude in sensitivity over current limits is obtained by a significant increase of the 136Xe mass, the monolithic and homogeneous configuration of the active medium, and the multiparameter measurements of the interactions enabled by the time projection chamber. Finally, the detector concept and anticipated performance are presented based upon demonstrated realizable background rates.
The COHERENT experiment is well poised to test sub-GeV dark matter models using detectors sensitive to coherent elastic neutrino-nucleus scattering (CEvNS) in the π+ decay-at-rest (π-DAR) neutrino ...beam produced by the Spallation Neutron Source. We show a planned 750-kg single-phase liquid argon scintillation detector would place leading limits on scalar light dark matter models for dark matter particles produced through vector and leptophobic portals in the absence of other effects beyond the standard model. The characteristic timing profile of a π-DAR beam allows a unique opportunity for constraining systematic uncertainties on the standard model background using a time window where dark matter signal is not expected, enhancing expected sensitivity. Additionally, we discuss future prospects which show that an on-axis CEvNS detector would probe the thermal abundance for a scalar dark matter candidate for all couplings α′ ≤ 1 for 15 MeV dark matter with just 1.0 tonne-yr of exposure with increased exposure testing a wider range of dark matter masses and spins.
Many extensions of the standard model of particle physics suggest that neutrinos should be Majorana-type fermions-that is, that neutrinos are their own anti-particles-but this assumption is difficult ...to confirm. Observation of neutrinoless double-β decay (0νββ), a spontaneous transition that may occur in several candidate nuclei, would verify the Majorana nature of the neutrino and constrain the absolute scale of the neutrino mass spectrum. Recent searches carried out with (76)Ge (the GERDA experiment) and (136)Xe (the KamLAND-Zen and EXO (Enriched Xenon Observatory)-200 experiments) have established the lifetime of this decay to be longer than 10(25) years, corresponding to a limit on the neutrino mass of 0.2-0.4 electronvolts. Here we report new results from EXO-200 based on a large (136)Xe exposure that represents an almost fourfold increase from our earlier published data sets. We have improved the detector resolution and revised the data analysis. The half-life sensitivity we obtain is 1.9 × 10(25) years, an improvement by a factor of 2.7 on previous EXO-200 results. We find no statistically significant evidence for 0νββ decay and set a half-life limit of 1.1 × 10(25) years at the 90 per cent confidence level. The high sensitivity holds promise for further running of the EXO-200 detector and future 0νββ decay searches with an improved Xe-based experiment, nEXO.
Coherent elastic neutrino-nucleus scattering (CEvNS) is calculated to be the dominant neutrino scattering channel for neutrinos of energy Eν<100 MeV. We report a limit for this process from data ...collected in an engineering run of the 29 kg CENNS-10 liquid argon detector located 27.5 m from the pion decay-at-rest neutrino source at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) with 4.2×1022 protons on target. The dataset provided constraints on beam-related backgrounds critical for future measurements and yielded <7.4 candidate CEvNS events which implies a cross section for the process, averaged over the SNS pion decay-at-rest flux, of <3.4×10−39 cm2, a limit within twice the Standard Model prediction. This is the first limit on CEvNS from an argon nucleus and confirms the earlier CsINa nonstandard neutrino interaction constraints from the collaboration. This run demonstrated the feasibility of the ongoing experimental effort to detect CEvNS with liquid argon.
The PROSPECT reactor antineutrino experiment Ashenfelter, J.; Balantekin, A.B.; Baldenegro, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2019, Letnik:
922
Journal Article
Recenzirano
Odprti dostop
The Precision Reactor Oscillation and Spectrum Experiment, PROSPECT, is designed to make both a precise measurement of the antineutrino spectrum from a highly-enriched uranium reactor and to probe ...eV-scale sterile neutrinos by searching for neutrino oscillations over meter-long baselines. PROSPECT utilizes a segmented6Li-doped liquid scintillator detector for both efficient detection of reactor antineutrinos through the inverse beta decay reaction and excellent background discrimination. PROSPECT is a movable 4-ton antineutrino detector covering distances of 7m to 13m from the High Flux Isotope Reactor core. It will probe the best-fit point of the ν̄e disappearance experiments at 4σ in 1 year and the favored regions of the sterile neutrino parameter space at more than 3σ in 3 years. PROSPECT will test the origin of spectral deviations observed in recent θ13 experiments, search for sterile neutrinos, and address the hypothesis of sterile neutrinos as an explanation of the reactor anomaly. This paper describes the design, construction, and commissioning of PROSPECT and reports first data characterizing the performance of the PROSPECT antineutrino detector.
The COHERENT Collaboration searched for scalar dark matter particles produced at the Spallation Neutron Source with masses between 1 and 220 MeV/c^{2} using a CsINa scintillation detector sensitive ...to nuclear recoils above 9 keV_{nr}. No evidence for dark matter is found and we thus place limits on allowed parameter space. With this low-threshold detector, we are sensitive to coherent elastic scattering between dark matter and nuclei. The cross section for this process is orders of magnitude higher than for other processes historically used for accelerator-based direct-detection searches so that our small, 14.6 kg detector significantly improves on past constraints. At peak sensitivity, we reject the flux consistent with the cosmologically observed dark-matter concentration for all coupling constants α_{D}<0.64, assuming a scalar dark-matter particle. We also calculate the sensitivity of future COHERENT detectors to dark-matter signals which will ambitiously test multiple dark-matter spin scenarios.
This Letter reports the first measurement of the 235U $\bar{ν}$e energy spectrum by PROSPECT, the Precision Reactor Oscillation and Spectrum experiment, operating 7.9 m from the 85 MWth highly ...enriched uranium (HEU) High Flux Isotope Reactor. With a surface-based, segmented detector, PROSPECT has observed 31678±304(stat) $\bar{ν}$e-induced inverse beta decays, the largest sample from HEU fission to date, 99% of which are attributed to 235U. Despite broad agreement, comparison of the Huber 235U model to the measured spectrum produces a χ2/ndf=51.4/31, driven primarily by deviations in two localized energy regions. The measured 235U spectrum shape is consistent with a deviation relative to prediction equal in size to that observed at low-enriched uranium power reactors in the $\bar{ν}$e energy region of 5–7 MeV.
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