R. A. Johnson
A5020844248- Particle physics theoretical and experimental studies
- Neutrino Physics Research
- Astrophysics and Cosmic Phenomena
- Dark Matter and Cosmic Phenomena
- Quantum Chromodynamics and Particle Interactions
- High-Energy Particle Collisions Research
- Particle Detector Development and Performance
- Metal and Thin Film Mechanics
- Fusion materials and technologies
- Radiation Detection and Scintillator Technologies
- Microstructure and mechanical properties
- Atomic and Subatomic Physics Research
- Nuclear Materials and Properties
- Particle accelerators and beam dynamics
- nanoparticles nucleation surface interactions
- Ion-surface interactions and analysis
- Muon and positron interactions and applications
- Surface and Thin Film Phenomena
- Advanced Chemical Physics Studies
- Membrane Separation Technologies
- Marine and coastal plant biology
- Advanced Materials Characterization Techniques
- Microstructure and Mechanical Properties of Steels
- Nuclear Physics and Applications
- Copper Interconnects and Reliability
University of Cincinnati
2015-2024
Colorado State University
2023
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
2023
University of Wisconsin–Madison
2022-2023
Iowa State University
1965-2023
University of Florida
2015-2022
Sea Turtle Conservancy
2017-2022
ExxonMobil (United States)
2004-2022
Toronto Zoo
2021
Pakistan Institute of Nuclear Science and Technology
2020
Recent molecular dynamics simulations of the growth $[{\mathrm{Ni}}_{0.8}{\mathrm{Fe}}_{0.2}/\mathrm{Au}]$ multilayers have revealed formation misfit-strain-reducing dislocation structures very similar to those observed experimentally. Here we report showing edge dislocations near interfaces vapor-deposited (111) [NiFe/CoFe/Cu] multilayers. Unlike misfit that accommodate lattice mismatch, here increase mismatch strain energy. Stop-action observations dynamically evolving atomic indicate...
A simple analytic nearest-neighbor embedded-atom-method model developed for monatomic fcc metals has been extended to study alloying. The two-body potential between different species of atoms is taken as a function the potentials pure with unique form which yields alloy models same invariance electron density transformations models. With several approximations, all parameters are given by experimentally measured physical quantities. dilute-limit heats solution binary alloys Cu, Ag, Au, Ni,...
The migration energies and atomic configurations for mono- di-interstitials divacancies in $\ensuremath{\alpha}$ iron have been calculated using a classical model. About 530 atoms surrounding the defect were treated as individual particles, each with three degrees of freedom, while remainder crystal was an elastic continuum imbedded it. A two-body central force devised which matched moduli, sharply repulsive at close separation, went to zero midway between second third neighboring atoms....
The implications of the mathematical format embedded-atom method computer modeling metals have been studied with use a simple nearest-neighbor analytic model for fcc lattice. physical inputs into are atomic volume, cohesive energy, bulk modulus, average shear vacancy-formation and slope at distance spherically averaged free-atom electron density calculated Hartree-Fock theory. employs an exponential repulsion between nearest-neighboring atoms, exponentially decreasing function density,...
The NuTeV Collaboration has extracted the electroweak parameter sin(2)theta(W) from measurement of ratios neutral current to charged nu and (-)nu cross sections. Our value, sin(2)theta((on-shell))(W) = 0.2277 +/- 0.0013(stat) 0.0009(syst), is 3 standard deviations above model prediction. We also present a independent analysis same data in terms neutral-current quark couplings.
The MiniBooNE experiment at Fermilab reports results from an analysis of $\bar \nu_e$ appearance data $11.27 \times 10^{20}$ protons on target in antineutrino mode, increase approximately a factor two over the previously reported results. An event excess $78.4 \pm 28.5$ events ($2.8 \sigma$) is observed energy range $200<E_\nu^{QE}<1250$ MeV. If interpreted two-neutrino oscillation model, $\bar{\nu}_{\mu}\rightarrow\bar{\nu}_e$, best fit to has probability 66% while background-only...
The MiniBooNE Collaboration reports first results of a search for $\nu_e$ appearance in $\nu_\mu$ beam. With two largely independent analyses, we observe no significant excess events above background reconstructed neutrino energies 475 MeV. data are consistent with oscillations within appearance-only oscillation model.
The MiniBooNE experiment at Fermilab reports results from an analysis of $\nu_e$ appearance data $12.84 \times 10^{20}$ protons on target in neutrino mode, increase approximately a factor two over previously reported results. A charged-current quasielastic event excess $381.2 \pm 85.2$ events ($4.5 \sigma$) is observed the energy range $200<E_\nu^{QE}<1250$~MeV. Combining these with $\bar \nu_e$ $11.27 antineutrino total plus $460.5 99.0$ ($4.7 observed. If interpreted two-neutrino...
The MiniBooNE experiment at Fermilab reports results from a search for ${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\overline{\ensuremath{\nu}}}_{e}$ oscillations, using data sample corresponding to $5.66\ifmmode\times\else\texttimes\fi{}{10}^{20}$ protons on target. An excess of $20.9\ifmmode\pm\else\textpm\fi{}14.0$ events is observed in the energy range $475<{E}_{\ensuremath{\nu}}^{\mathrm{QE}}<1250\text{ }\text{ }\mathrm{MeV}$, which, when constrained by...
A high-statistics sample of charged-current muon neutrino scattering events collected with the MiniBooNE experiment is analyzed to extract first measurement double differential cross section ($\frac{d^2\sigma}{dT_\mu d\cos\theta_\mu}$) for quasielastic (CCQE) on carbon. This result features minimal model dependence and provides most complete information this process date. With assumption CCQE scattering, absolute as a function energy ($\sigma[E_\nu]$) single ($\frac{d\sigma}{dQ^2}$) are...
The modified embedded atom method (MEAM) is an empirical extension of (EAM) that includes angular forces. MEAM, which has previously been applied to the atoms in FCC, BCC, and diamond cubic crystal systems, extended HCP structure. Parameters have determined for metals c/a ratios less than ideal. model fitted lattice constants, elastic cohesive energy, vacancy formation BCC-HCP structural energy difference these able reproduce this extensive data base quite well. Structural energies constants...
This paper describes the design and construction of MicroBooNE liquid argon time projection chamber associated systems. is first phase Short Baseline Neutrino program, located at Fermilab, will utilize capabilities detectors to examine a rich assortment physics topics. In this document details specifications, assembly procedures, acceptance tests are reported.
The MiniBooNE Collaboration observes unexplained electronlike events in the reconstructed neutrino energy range from 200 to 475 MeV. With $6.46\ifmmode\times\else\texttimes\fi{}{10}^{20}$ protons on target, 544 are observed this range, compared an expectation of $415.2\ifmmode\pm\else\textpm\fi{}43.4$ events, corresponding excess $128.8\ifmmode\pm\else\textpm\fi{}20.4\ifmmode\pm\else\textpm\fi{}38.3$ events. shape several kinematic variables is consistent with being due either...
A kinetic model has been designed to study substitutional solute segregation during irradiation in facecentered-cubic metals. The includes a 100> split interstitial binding impurities second-neighbor distances, vacancy first-neighbor and the possibility of migration bound complexes. Also taken into account are effects diffusional encounters with spatially independent reaction terms. resultant rate equations have solved numerically for thin-foil geometry as function time different...
The Booster Neutrino Experiment (MiniBooNE) searches for numu-to-nue oscillations using the O(1 GeV) neutrino beam produced by synchrotron at Fermi National Accelerator Laboratory (FNAL). delivers protons with 8 GeV kinetic energy (8.89 GeV/c momentum) to a beryllium target, producing neutrinos from decay of secondary particles in line. We describe Monte Carlo simulation methods used estimate flux beamline incident on MiniBooNE detector both polarities focussing horn. uses Geant4 framework...
A measurement of the energy dependence antineutrino disappearance at Daya Bay reactor neutrino experiment is reported. Electron antineutrinos (ν¯(e)) from six 2.9 GW(th) reactors were detected with detectors deployed in two near (effective baselines 512 and 561 m) one far (1579 underground experimental halls. Using 217 days data, 41 589 (203 809 92 912) candidates hall (near halls). An improved oscillation amplitude sin(2)2θ(13)=0.090(-0.009)(+0.008) first direct ν¯(e) mass-squared...
We report an improved measurement of the neutrino mixing angle $\theta_{13}$ from Daya Bay Reactor Neutrino Experiment. exclude a zero value for $\sin^22\theta_{13}$ with significance 7.7 standard deviations. Electron antineutrinos six reactors 2.9 GW$_{\rm th}$ were detected in antineutrino detectors deployed two near (flux-weighted baselines 470 m and 576 m) one far (1648 underground experimental halls. Using 139 days data, 28909 (205308) electron candidates at hall (near halls). The ratio...
The MiniBooNE experiment at Fermilab reports results from an analysis of the combined $ν_e$ and $\bar ν_e$ appearance data $6.46 \times 10^{20}$ protons on target in neutrino mode $11.27 antineutrino mode. A total excess $240.3 \pm 34.5 52.6$ events ($3.8 σ$) is observed combining two sets energy range $200
This Letter reports a measurement of the flux and energy spectrum electron antineutrinos from six 2.9~GW$_{th}$ nuclear reactors with detectors deployed in two near (effective baselines 512~m 561~m) one far (1,579~m) underground experimental halls Daya Bay experiment. Using 217 days data, 296,721 41,589 inverse beta decay (IBD) candidates were detected halls, respectively. The measured IBD yield is (1.55 $\pm$ 0.04) $\times$ 10$^{-18}$~cm$^2$/GW/day or (5.92 0.14) 10$^{-43}$~cm$^2$/fission....
We report a new measurement of electron antineutrino disappearance using the fully constructed Daya Bay Reactor Neutrino Experiment. The final two eight detectors were installed in summer 2012. Including 404 days data collected from October 2012 to November 2013 resulted total exposure 6.9×10^{5} GW_{th} ton days, 3.6 times increase over our previous results. Improvements energy calibration limited variations between 0.2%. Removal six ^{241}Am-^{13}C radioactive sources reduced background by...
The Daya Bay Collaboration reports precise measurements of the ${\ensuremath{\theta}}_{13}$ neutrino mixing angle and predicts $\mathrm{\ensuremath{\Delta}}\phantom{\rule{0}{0ex}}{m}_{32}^{2}$ mass difference for both normal inverted hierarchy scenarios. These values are based on comparing detection antineutrinos by ''near'' ''far'' detectors more than 2.5 million inverse beta-decay observations.