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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Evidence for Astrophysical Muon Neutrinos from the Northern Sky with IceCube
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Constraints on Ultrahigh-Energy Cosmic-Ray Sources from a Search for Neutrinos above 10 PeV with IceCube
In this study, we report constraints on the sources of ultra-high-energy cosmic ray (UHECR) above 10 9 GeV , based on an analysis of seven years of IceCube data. This analysis efficiently selects very high energy neutrino-induced events which have deposited energies from 5 X 10 5 GeV to above 10 11 GeV . Two neutrino-induced events with an estimated deposited energy of (2.6±0.3)×10 6 GeV , the highest neutrino energies observed so far, and (7.7±2.0)×10 5 GeV were detected. The atmospheric background-only hypothesis of detecting these events is rejected at 3.6σ . The hypothesis that the observed events are of cosmogenic origin is also rejected at > 99% CL because of the limited deposited energy and the non-observation of events at higher energy, while their observation is consistent with an astrophysical origin. Our limits on cosmogenic neutrino fluxes disfavor the UHECR sources having cosmological evolution stronger than the star formation rate, e.g., active galactic nuclei and $γ$-ray bursts, assuming proton-dominated UHECRs. Constraints on UHECR sources including mixed and heavy UHECR compositions are obtained for models of neutrino production within UHECR sources. Our limit disfavors a significant part of parameter space for active galactic nuclei and new-born pulsar models.
Measurement of Atmospheric Neutrino Oscillations at 6–56 GeV with IceCube DeepCore
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Constraints on Minute-Scale Transient Astrophysical Neutrino Sources
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Search for Spontaneous Radiation from Wave Function Collapse in the Majorana Demonstrator
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Search for Solar Axions via Axion-Photon Coupling with the Majorana Demonstrator
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Final Result of the Majorana Demonstrator’s Search for Neutrinoless Double- β Decay in Ge 76
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Erratum: Search for Spontaneous Radiation from Wave Function Collapse in the Majorana Demonstrator [Phys. Rev. Lett. 129 , 080401 (2022)]
This corrects the article DOI: 10.1103/PhysRevLett.129.080401.
Constraints on the Decay of 180𝑚 Ta
180m Ta is a rare nuclear isomer whose decay has never been observed. Its remarkably long lifetime surpasses the half-lives of all other known β and electron capture decays due to the large K-spin differences and small energy differences between the isomeric and lower energy states. Detecting its decay presents a significant experimental challenge but could shed light on neutrino-induced nucleosynthesis mechanisms, the nature of dark matter and K-spin violation. For this study, we repurposed the Majorana Demonstrator, an experimental search for the neutrinoless double-beta decay of 76 Ge using an array of high-purity germanium detectors, to search for the decay of 180m Ta. More than 17 kilograms, the largest amount of tantalum metal ever used for such a search was installed within the ultra-low background Majorana Demonstrator detector array. In this paper we present results from the first year of Ta data taking and provide an updated limit for the 180m Ta half-life on the different decay channels. With new limits up to 1.5 × 10 19 years, we improved existing limits by one to two orders of magnitude. Furthermore, this result is the most sensitive search for a single β and electron capture decay ever achieved.
Exotic Dark Matter Search with the Majorana Demonstrator
With excellent energy resolution and ultralow-level radiogenic backgrounds, the high-purity germanium detectors in the enable searches for several classes of exotic dark matter (DM) models. In this work, we report new experimental limits on keV-scale sterile neutrino DM via the transition magnetic moment from conversion to active neutrinos ν s → ν a . We report new limits on fermionic dark matter absorption ( χ + A → ν + A ) and sub-GeV DM-nucleus 3 → 2 scattering ( χ + χ + A → ϕ + A ), and new exclusion limits for bosonic dark matter (axionlike particles and dark photons). These searches utilize the (1–100)-keV low-energy region of a 37.5-kg y exposure collected by the between May 2016 and November 2019 using a set of Ge 76 -enriched detectors whose surface exposure time was carefully controlled, resulting in extremely low levels of cosmogenic activation. Published by the American Physical Society 2024
Final Results of the M AJORANA D EMONSTRATOR ’s Search for Double-Beta Decay of 76 Ge to Excited States of 76 Se
76 Ge can 𝛽𝛽 decay into three possible excited states of 76 Se , with the emission of two or, if the neutrino is Majorana, zero neutrinos. None of these six transitions have yet been observed. The M AJORANA D EMONSTRATOR was designed to study 𝛽𝛽 decay of 76 Ge using a low background array of high purity germanium detectors. With 98.2 kg-y of isotopic exposure, the demonstrator sets the strongest half-life limits to date for all six transition modes. For 2𝜈𝛽𝛽 to the 0$^+_1$ state of 76 Se , this search has begun to probe for the first time half-life values predicted using modern many-body nuclear theory techniques, setting a limit of 𝑇 1/2 > 1.5 × 10 24 y (90% CL).
Economic Competitiveness of U.S. Utility-Scale Photovoltaics Systems in 2015: Regional Cost Modeling of Installed Cost ($/W) and LCOE ($/kWh)
Utility-scale photovoltaics (PV) system growth is largely driven by the economic metrics of total installed costs and levelized cost of electricity (LCOE), which differ by region. This study details regional cost factors, including environment (wind speed and snow loads), labor costs, material costs, sales taxes, and permitting costs using a new system-level bottom-up cost modeling approach. We use this model to identify regional all-in PV installed costs for fixed-tilt and one-axis tracker systems in the United States with consideration of union and non-union labor costs in 2015. LCOEs using those regional installed costs are then modeled and spatially presented. Finally, we assess the cost reduction opportunities of increasing module conversion efficiencies on PV system costs in order to indicate the possible economic impacts of module technology advancements and help future research and development (R&D) effects in the context of U.S. SunShot targets.
ADC Nonlinearity Correction for the Majorana Demonstrator
Imperfections in analog-to-digital conversion cannot be ignored when signal digitization requirements demand both wide dynamic range and high resolution, as is the case for the MAJORANA DEMONSTRATOR 76 Ge neutrinoless double beta decay search. Enabling the experiment's high-resolution spectral analysis and efficient pulse shape discrimination required careful measurement and correction of ADC nonlinearites. Here, a simple measurement protocol was developed that did not require sophisticated equipment or lengthy data taking campaigns. A slope-dependent hysteresis was observed and characterized. A correction applied to digitized waveforms prior to signal processing reduced the differential and integral nonlinearites by an order of magnitude, eliminating these as dominant contributions to the systematic energy uncertainty at the double-beta decay Q value.
Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A
Previous detections of individual astrophysical sources of neutrinos are limited to the Sun and the supernova 1987A, whereas the origins of the diffuse flux of high-energy cosmic neutrinos remain unidentified. On 22 September 2017, we detected a high-energy neutrino, IceCube-170922A, with an energy of ~290 tera–electron volts. Its arrival direction was consistent with the location of a known γ-ray blazar, TXS 0506+056, observed to be in a flaring state. An extensive multiwavelength campaign followed, ranging from radio frequencies to γ-rays. These observations characterize the variability and energetics of the blazar and include the detection of TXS 0506+056 in very-high-energy γ-rays. We report this observation of a neutrino in spatial coincidence with a γ-ray–emitting blazar during an active phase suggests that blazars may be a source of high-energy neutrinos.
Experiments towards a neutron target for measurements in inverse kinematics
Neutron-induced reactions play an important role in fundamental nuclear physics, nuclear astrophysics, and applications. In the case of reactions on rare isotopes, there are limited options for direct experimental measurements. The Neutron Target Demonstrator project at Los Alamos National Laboratory seeks to test the feasibility of moderating spallation neutrons within a 1 m 3 graphite cube to create a standing neutron target for neutron-induced reaction measurements in inverse kinematics. This paper presents the results of experimental neutron flux distribution tests using neutron sources (ranging from 1 keV to 50 MeV) created by accelerators at the University of Notre Dame and Texas A&M University. Measurements were made with both the full graphite cube as well as a ”half cube” setup in which half of the graphite cube was removed. The measured distributions agree with simulated distributions in the case of the full cube moderator, although there remain discrepancies in certain cases for the half cube moderator. The results shown here will provide useful information for an upcoming experimental campaign to test the neutron target proof-of-principle.
Development of a general analysis and unfolding scheme and its application to measure the energy spectrum of atmospheric neutrinos with IceCube: IceCube Collaboration
Here we present the development and application of a generic analysis scheme for the measurement of neutrino spectra with the IceCube detector. This scheme is based on regularized unfolding, preceded by an event selection which uses a Minimum Redundancy Maximum Relevance algorithm to select the relevant variables and a random forest for the classification of events. The analysis has been developed using IceCube data from the 59-string configuration of the detector. 27,771 neutrino candidates were detected in 346 days of livetime. A rejection of 99.9999 % of the atmospheric muon background is achieved. The energy spectrum of the atmospheric neutrino flux is obtained using the TRUEE unfolding program. The unfolded spectrum of atmospheric muon neutrinos covers an energy range from 100 GeV to 1 PeV. Compared to the previous measurement using the detector in the 40-string configuration, the analysis presented here, extends the upper end of the atmospheric neutrino spectrum by more than a factor of two, reaching an energy region that has not been previously accessed by spectral measurements.