M. P. Mendenhall
A5037945126- Atomic and Subatomic Physics Research
- Nuclear Physics and Applications
- Neutrino Physics Research
- Particle physics theoretical and experimental studies
- Radiation Detection and Scintillator Technologies
- Quantum, superfluid, helium dynamics
- Dark Matter and Cosmic Phenomena
- Nuclear reactor physics and engineering
- Astrophysics and Cosmic Phenomena
- Particle Detector Development and Performance
- Planetary Science and Exploration
- Advanced NMR Techniques and Applications
- Nuclear physics research studies
- Nuclear Materials and Properties
- Cold Atom Physics and Bose-Einstein Condensates
- Astro and Planetary Science
- Computational Fluid Dynamics and Aerodynamics
- Hydrogen Storage and Materials
- Image Processing and 3D Reconstruction
- Quantum Chromodynamics and Particle Interactions
- Radioactive Decay and Measurement Techniques
- Electron and X-Ray Spectroscopy Techniques
- X-ray Spectroscopy and Fluorescence Analysis
- Radioactive contamination and transfer
- Advanced Frequency and Time Standards
Lawrence Livermore National Laboratory
2017-2025
Argonne National Laboratory
2021
Tulane University
2017-2021
California Institute of Technology
2008-2020
National Institute of Standards and Technology
2015-2019
Vertex Pharmaceuticals (United States)
2017
Brookhaven National Laboratory
2016
University of Washington
2007
Washington University in St. Louis
2007
Nielsen Engineering & Research (United States)
2001-2006
The PROSPECT Collaboration presents their improved results with new limits on the oscillation of electron antineutrinos to light sterile neutrinos and energy spectrum measurements several short baselines.
This Letter reports the first scientific results from observation of antineutrinos emitted by fission products $^{235}\mathrm{U}$ at High Flux Isotope Reactor. PROSPECT, Precision Reactor Oscillation and Spectrum Experiment, consists a segmented 4 ton $^{6}\mathrm{Li}$-doped liquid scintillator detector covering baseline range 7--9 m reactor operating under less than 1 water equivalent overburden. Data collected during 33 live days operation nominal power 85 MW yield detection $25\text{...
A neutron $\ensuremath{\beta}$-decay asymmetry measurement using polarized ultracold neutrons (UCN) determines the correlation between spin of and momentum decay electron. The authors extract ratio weak axial-vector to vector couplings with reduced uncertainties. This new result from first this UCN contributes a benchmark for lattice QCD calculations possibility improved precision on CKM matrix element ${V}_{u\phantom{\rule{0}{0ex}}d}$ $\ensuremath{\beta}$ decay.
A new measurement of the neutron $β$-decay asymmetry $A_0$ has been carried out by UCNA collaboration using polarized ultracold neutrons (UCN) from solid deuterium UCN source at Los Alamos Neutron Science Center (LANSCE). Improvements in experiment have led to reductions both statistical and systematic uncertainties leading $A_0 = -0.11954(55)_{\rm stat.}(98)_{\rm syst.}$, corresponding ratio axial-vector vector coupling $λ\equiv g_A/g_V -1.2756(30)$.
The Precision Reactor Oscillation and Spectrum Experiment, PROSPECT, is designed to make a precise measurement of the antineutrino spectrum from highly-enriched uranium reactor probe eV-scale sterile neutrinos by searching for neutrino oscillations over meter-long distances. PROSPECT conceived as 2-phase experiment utilizing segmented $^6$Li-doped liquid scintillator detectors both efficient detection antineutrinos through inverse beta decay reaction excellent background discrimination....
If dark matter has mass lower than around 1 GeV, it will not impart enough energy to cause detectable nuclear recoils in many direct-detection experiments. However, if is upscattered high by collisions with cosmic rays, may be both experiments and neutrino We report the results of a dedicated search for boosted rays using PROSPECT reactor antineutrino experiment. show that such flux would display characteristic diurnal sidereal modulation, use this set new experimental constraints on sub-GeV...
In this paper, we describe the performance of Los Alamos spallation-driven solid-deuterium ultra-cold neutron (UCN) source. Measurements cold flux, very low energy production rate, and UCN rates density at exit from biological shield are presented compared to Monte Carlo predictions. The compare well with predictions code MCNPX agree our custom code. source is shown perform as modeled. maximum delivered 52(9) UCN/cc a solid deuterium volume ∼1500 cm3.
This Letter reports the first measurement of $^{235}$U $\overline{\nu_{e}}$ energy spectrum by PROSPECT, Precision Reactor Oscillation and Spectrum experiment, operating 7.9m from 85MW$_{\mathrm{th}}$ highly-enriched uranium (HEU) High Flux Isotope Reactor. With a surface-based, segmented detector, PROSPECT has observed 31678$\pm$304 (stat.) $\overline{\nu_{e}}$-induced inverse beta decays (IBD), largest sample HEU fission to date, 99% which are attributed $^{235}$U. Despite broad agreement,...
A cryogenic apparatus is described that enables a new experiment, nEDM@SNS, with major improvement in sensitivity compared to the existing limit search for neutron Electric Dipole Moment (EDM). This uses superfluid 4He produce high density of Ultra-Cold Neutrons (UCN) which are contained suitably coated pair measurement cells. The be operated at Spallation Neutron Source Oak Ridge National Laboratory, polarized 3He from an Atomic Beam injected into and transported cells where it serves as...
A precise measurement of the neutron decay β asymmetry A₀ has been carried out using polarized ultracold neutrons from pulsed spallation source at Los Alamos Neutron Science Center. Combining data obtained in 2008 and 2009, we report = -0.119 66±0.000 89{-0.001 40}{+0.001 23}, which determine ratio axial-vector to vector weak coupling nucleon g{A}/g{V}=-1.275 90{-0.004 45}{+0.004 09}.
We present a detailed report of measurement the neutron $\beta$-asymmetry parameter $A_0$, parity-violating angular correlation between spin and decay electron momentum, performed with polarized ultracold neutrons (UCN). UCN were extracted from pulsed spallation solid deuterium source via transport through 7-T magnetic field. The then transported an adiabatic-fast-passage spin-flipper field region, prior to storage in cylindrical volume situated within 1-T $2 \times 2\pi$ solenoidal...
It has been proposed recently that a previously unobserved neutron decay branch to dark matter particle ($\ensuremath{\chi}$) could account for the discrepancy in lifetime observed experiments use two different measurement techniques. One of possible final states discussed includes single $\ensuremath{\chi}$ along with an ${e}^{+}{e}^{\ensuremath{-}}$ pair. We data from UCNA (Ultracold Neutron Asymmetry) experiment set limits on this channel. Coincident electron-like events are detected...
We report the first result for electron-antineutrino angular correlation ($a$ coefficient) in free neutron $\ensuremath{\beta}$ decay from aCORN experiment. uses a novel method which $a$ coefficient is proportional to an asymmetry proton time of flight events where electron and recoil are detected delayed coincidence. Data presented 15 month run at NIST Center Neutron Research. obtained...
The aCORN experiment measures the neutron-decay electron-antineutrino correlation ($a$ coefficient) using a novel method based on an asymmetry in proton time-of-flight for events where beta electron and recoil are detected delayed coincidence. We report data analysis result from second run at NIST Center Neutron Research, high-flux cold neutron beam new NG-C guide end position:...
This Letter reports one of the most precise measurements to date antineutrino spectrum from a purely 235U-fueled reactor, made with final dataset PROSPECT-I detector at High Flux Isotope Reactor. By extracting information previously unused segments, this analysis effectively doubles statistics previous PROSPECT measurement. The reconstructed energy is unfolded into and compared both Huber-Mueller model commercial reactor burning multiple fuel isotopes. A local excess over observed in 5–7 MeV...
The PROSPECT and STEREO collaborations present a combined measurement of the pure ^{235}U antineutrino spectrum, without site specific corrections or detector-dependent effects. spectral measurements two highest precision experiments at research reactors are found to be compatible with χ^{2}/ndf=24.1/21, allowing joint unfolding prompt energy into energy. This ν[over ¯]_{e} spectrum is provided community, an excess events relative Huber model in 5-6 MeV region. When Gaussian bump fitted...
This paper describes the design and performance of a 50 liter, two-segment $^{6}$Li-loaded liquid scintillator detector that was designed operated as prototype for PROSPECT (Precision Reactor Oscillation Spectrum) Experiment. The constructed according to specifications experiment. It features low-mass optical separators, an integrated source calibration system, materials are compatible with $^{6}$Li-doped developed by PROSPECT. We demonstrate high light collection 850$\pm$20 PE/MeV, energy...
The Ultracold Neutron Asymmetry (UCNA) experiment was designed to measure the $\beta$-decay asymmetry parameter, $A_0$, for free neutron decay. In experiment, polarized ultracold neutrons are transported into a decay trap, and their electrons detected with $\approx 4\pi$ acceptance two detector packages which provide position energy reconstruction. also has sensitivity $b_{n}$, Fierz interference term in rate. this work, we determine $b_{n}$ from dependence of $A_0$ using data taken during...
We report the first measurement of an angular correlation parameter in neutron $\ensuremath{\beta}$ decay using polarized ultracold neutrons (UCN). utilize UCN with energies below about 200 neV, which we guide and store for $\ensuremath{\sim}30\text{ }\text{ }\mathrm{s}$ a Cu volume. The interaction magnetic dipole moment static 7 T field external to volume provides 420 neV potential energy barrier spin state parallel field, polarizing before they pass through adiabatic fast passage flipper...