J. F. Wilkerson
A5080130360- Neutrino Physics Research
- Particle physics theoretical and experimental studies
- Astrophysics and Cosmic Phenomena
- Dark Matter and Cosmic Phenomena
- Particle Detector Development and Performance
- Radiation Detection and Scintillator Technologies
- Nuclear Physics and Applications
- Particle accelerators and beam dynamics
- Atomic and Subatomic Physics Research
- Nuclear physics research studies
- Muon and positron interactions and applications
- Atomic and Molecular Physics
- Nuclear reactor physics and engineering
- Particle Accelerators and Free-Electron Lasers
- Atmospheric Ozone and Climate
- Radioactive Decay and Measurement Techniques
- Magnetic confinement fusion research
- Quantum, superfluid, helium dynamics
- Advanced NMR Techniques and Applications
- Scientific Research and Discoveries
- Quantum Chromodynamics and Particle Interactions
- Cosmology and Gravitation Theories
- CCD and CMOS Imaging Sensors
- Geophysical Methods and Applications
- Advanced Chemical Physics Studies
University of North Carolina at Chapel Hill
2016-2025
Triangle Universities Nuclear Laboratory
2015-2025
Oak Ridge National Laboratory
2014-2024
Institute for Nuclear Research
1991-2022
Campbell Collaboration
2022
University of Tennessee at Knoxville
2021
Osys Technology
2021
U.S. Army Engineer Research and Development Center
2021
Louisiana Department of Wildlife and Fisheries
2021
University of Washington
2009-2020
We report on several features in the energy spectrum from an ultralow-noise germanium detector operated deep underground. By implementing a new technique able to reject surface events, number of cosmogenic peaks can be observed for first time. discuss irreducible excess bulklike events below 3 keV ionization energy. These could caused by unknown backgrounds, but also dark matter interactions consistent with DAMA/LIBRA. It is not yet possible determine their origin. Improved constraints are...
We review and analyze the available information on nuclear-fusion cross sections that are most important for solar energy generation neutrino production. provide best values low-energy cross-section factors and, wherever possible, estimates of uncertainties. also describe experiments calculations required in order to improve our knowledge fusion rates.DOI:https://doi.org/10.1103/RevModPhys.70.1265©1998 American Physical Society
The Russian-American experiment SAGE began to measure the solar neutrino capture rate with a target of gallium metal in December 1989. Measurements have continued only few brief interruptions since that time. In this article we present experimental improvements its last published data summary 2001. Assuming production was constant during period collection, combined analysis 168 extractions through 2007 gives neutrinos energy more than 233 keV $65.{4}_{\ensuremath{-}3.0}^{+3.1}$ (stat)...
The solar neutrino capture rate measured by the Russian-American Gallium Experiment (SAGE) on metallic gallium during period January 1990 through December 1997 is ${67.2}_{\ensuremath{-}7.0\ensuremath{-}3.0}^{+7.2+3.5}$ SNU, where uncertainties are statistical and systematic, respectively. This represents only about half of predicted standard model 129 SNU. All experimental procedures, including extraction germanium from gallium, counting ${}^{71}\mathrm{Ge},$ data analysis, discussed in detail.
Fifteen months of cumulative CoGeNT data are examined for indications an annual modulation, a predicted signature weakly interacting massive particle (WIMP) interactions. Presently available support the presence modulated component unknown origin, with parameters prima facie compatible galactic halo composed light-mass WIMPs. Unoptimized estimators yield statistical significance modulation ∼2.8σ, limited by short exposure.
The M ajorana D emonstrator will search for the neutrinoless double-beta<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mo stretchy="false">(</mml:mo><mml:mi>β</mml:mi><mml:mi>β</mml:mi><mml:mfenced separators="|"><mml:mrow><mml:mn fontstyle="italic">0</mml:mn><mml:mi>ν</mml:mi></mml:mrow></mml:mfenced><mml:mo stretchy="false">)</mml:mo></mml:math>decay of isotope<mml:math id="M2"/>Ge with a mixed array enriched and natural germanium detectors. observation this rare...
The Baksan Experiment on Sterile Transitions (BEST) was designed to investigate the deficit of electron neutrinos ν_{e} observed in previous gallium-based radiochemical measurements with high-intensity neutrino sources, commonly referred as "gallium anomaly," which could be interpreted evidence for oscillations between and sterile (ν_{s}) states. A 3.414-MCi ^{51}Cr source placed at center two nested Ga volumes were made production ^{71}Ge through charged current reaction,...
The Majorana Demonstrator searched for neutrinoless double-β decay (0νββ) of ^{76}Ge using modular arrays high-purity Ge detectors operated in vacuum cryostats a low-background shield. with up to 40.4 kg (27.2 enriched ∼88% ^{76}Ge). From these measurements, the has accumulated 64.5 yr active exposure. With world-leading energy resolution 2.52 keV FWHM at 2039 Q_{ββ} (0.12%), we set half-life limit 0νββ T_{1/2}>8.3×10^{25} (90% C.L.). This provides range upper limits on m_{ββ} (113-269) meV...
A radiochemical $^{71}\mathrm{\ensuremath{-}}^{71}$Ge experiment using 30 tons of gallium to determine the primary flux neutrinos from Sun has begun operation at Baksan Neutrino Observatory in U.S.S.R. Assuming that extraction efficiency for $^{71}\mathrm{Ge}$ atoms produced by solar is same as natural Ge carrier, we observed capture rate be ${20}_{\mathrm{\ensuremath{-}}20}^{+15}$(stat)\ifmmode\pm\else\textpm\fi{}32(syst) neutrino units (SNU), resulting a limit less than 79 SNU (90% C.L.)....
The solar neutrino capture rate measured by SAGE is well below that predicted models. To check the overall experimental efficiency, we exposed 13 tonnes of Ga metal to a reactor-produced 517 kCi source ${}^{51}$Cr. ratio production from activity $0.95\ifmmode\pm\else\textpm\fi{}0.11(\mathrm{stat})+0.05/\ensuremath{-}0.08(\mathrm{syst})$. This agreement verifies efficiency correctly, establishes there are no unknown systematic errors at 10% level, and provides considerable evidence for...
The neutrino capture rate measured by the Russian-American Gallium Experiment is well below that predicted solar models. To check response of this experiment to low-energy neutrinos, a 517 kCi source ${}^{51}$Cr was produced irradiating 512.7 g 92.4%-enriched ${}^{50}$Cr in high-flux fast neutron reactor. This source, which mainly emits monoenergetic 747-keV placed at center 13.1 ton target liquid gallium and cross section for production ${}^{71}$Ge inverse beta decay $\mathrm{reaction}{...
An intense source of $^{37}\mathrm{Ar}$ was produced by the $(n,\ensuremath{\alpha})$ reaction on $^{40}\mathrm{Ca}$ irradiating 330 kg calcium oxide in fast neutron breeder reactor at Zarechny, Russia. The released from solid target dissolution acid, collected this solution, purified, sealed into a small source, and brought to Baksan Neutrino Observatory where it used irradiate 13 tonnes gallium metal Russian-American solar neutrino experiment SAGE. Ten exposures whose initial strength...
A claim for evidence of dark matter interactions in the DAMA experiment has been recently reinforced. We employ a new type germanium detector to conclusively rule out standard isothermal galactic halo weakly interacting massive particles as explanation annual modulation effect leading claim. Bounds are similarly imposed on suggestion that pseudoscalars might lead effect. describe sensitivity light achievable with our device, particular, next-to-minimal supersymmetric model candidates.
The Majorana Collaboration is operating an array of high-purity Ge detectors to search for the neutrinoless double-$\ensuremath{\beta}$ decay $^{76}\mathrm{Ge}$. Demonstrator consists 44.1 kg (29.7 enriched 88% in $^{76}\mathrm{Ge}$) split between two modules constructed from ultraclean materials. Both are contained a low-background shield at Sanford Underground Research Facility Lead, South Dakota. We present updated results on $^{76}\mathrm{Ge}$ with $26.0\ifmmode\pm\else\textpm\fi{}0.5$...
First results from the BEST Collaboration searching for short-baseline neutrino oscillations to sterile neutrinos with a high-intensity ${}^{51}$Cr monoenergetic source reaffirm that so-called gallium anomaly, deficit in electron neutrinos, persists. $4\ensuremath{\sigma}$ deficits were observed ${}^{71}$Ge production rates at two different distance scales, which could be interpreted as between an and hypothetical neutrino. The are consistent mass squared difference above about 0.5...
The Majorana Demonstrator neutrinoless double-beta decay experiment comprises a 44 kg (30 enriched in ^{76}Ge) array of p-type, point-contact germanium detectors. With its unprecedented energy resolution and ultralow backgrounds, also searches for rare event signatures from beyond standard model physics the low region below 100 keV. In this Letter, we test continuous spontaneous localization (CSL) model, one mathematically well-motivated wave function collapse models aimed at solving...
With the compelling evidence for massive neutrinos from recent v-oscillation experiments, one of most fundamental tasks particle physics over next years will be determination absolute mass scale neutrinos. The value v-masses have crucial implications cosmology, astrophysics and physics. We present case a generation tritium β decay experiment to perform high precision direct measurement electron neutrino with sub-eV sensitivity. discuss experimental requirements technical challenges proposed...
We report the most sensitive direct upper limit set on mass ${\mathit{m}}_{\ensuremath{\nu}}$ of electron antineutrino. Our measurements shape \ensuremath{\beta} decay spectrum free molecular tritium yield, under assumption no new physics other than that mass, a central value for ${\mathit{m}}_{\ensuremath{\nu}}^{2}$ -147\ifmmode\pm\else\textpm\fi{}68\ifmmode\pm\else\textpm\fi{}41 ${\mathrm{eV}}^{2}$, which corresponds to an 9.3 eV (95% confidence level) ${\mathit{m}}_{\ensuremath{\nu}}$....
The Russian-American solar neutrino experiment has measured the capture rate of neutrinos on metallic gallium in a radiochemical at Baksan Neutrino Observatory. Eight years measurement give result ${67.2}_{\ensuremath{-}7.0\ensuremath{-}3.0}^{+7.2+3.5}$ units, where uncertainties are statistical and systematic, respectively. restrictions these results impose vacuum oscillation parameters given.
We comment on the recent claim for experimental observation of neutrinoless double-beta decay. discuss several limitations in analysis provided that paper and conclude there is no basis presented claim.
We present new limits on exotic keV-scale physics based 478 kg d of Majorana Demonstrator commissioning data. Constraints at the 90% confidence level are derived bosonic dark matter (DM) and solar axion couplings, Pauli exclusion principle violating (PEPV) decay, electron decay using monoenergetic peak signal above our background. Our most stringent DM constraints set for 11.8 keV mass particles, limiting g_{Ae}<4.5×10^{-13} pseudoscalars (α^{'}/α)<9.7×10^{-28} vectors. also report a 14.4...