D. Melconian
A5030460055- Atomic and Subatomic Physics Research
- Nuclear physics research studies
- Particle physics theoretical and experimental studies
- Neutrino Physics Research
- Nuclear Physics and Applications
- Quantum Chromodynamics and Particle Interactions
- Quantum, superfluid, helium dynamics
- Cold Atom Physics and Bose-Einstein Condensates
- Dark Matter and Cosmic Phenomena
- Atomic and Molecular Physics
- Radioactive Decay and Measurement Techniques
- Radiation Detection and Scintillator Technologies
- Advanced Frequency and Time Standards
- Particle accelerators and beam dynamics
- Advanced NMR Techniques and Applications
- Nuclear reactor physics and engineering
- Astronomical and nuclear sciences
- Spacecraft and Cryogenic Technologies
- Particle Accelerators and Free-Electron Lasers
- Gyrotron and Vacuum Electronics Research
- Space Satellite Systems and Control
- Advanced Chemical Physics Studies
- Astronomical Observations and Instrumentation
- Astrophysics and Cosmic Phenomena
- Quantum Mechanics and Applications
Texas A&M University
2014-2024
University of Washington
2006-2019
Mitchell Institute
2009-2015
University of Maryland, College Park
2013
TRIUMF
1998-2011
Tel Aviv University
2011
Simon Fraser University
1998-2009
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.
We have set limits on contributions of scalar interactions to nuclear $\ensuremath{\beta}$ decay. A magneto-optical trap provides a localized source atoms suspended in space, so the low-energy recoiling nuclei can freely escape and be detected coincidence with $\ensuremath{\beta}$. This allows reconstruction neutrino momentum, measurement $\ensuremath{\beta}\mathrm{\text{\ensuremath{-}}}\ensuremath{\nu}$ correlation, more direct fashion than previously possible. The correlation parameter...
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 $λ\equiv g_A/g_V -1.2756(30)$.
We present precision measurements of the 3He + 4He --> 7Be reaction in range ECM = 0.33 to 1.23 MeV using a small gas cell and detection both prompt gamma rays activity. Our activity are good agreement within an experimental uncertainty several percent. find S(0) 0.595 +/- 0.018 keV b from fits Kajino theory our data. compare results with published measurements, we discuss consequences for Big Bang Nucleosynthesis solar neutrino flux calculations.
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.
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...
Using Triumf's neutral atom trap, Trinat, for nuclear β decay, we have measured the asymmetry with respect to initial spin in ^{37}K be A_{β}=-0.5707(13)_{syst}(13)_{stat}(5)_{pol}, a 0.3% measurement. This is best relative accuracy of any β-asymmetry measurement nucleus or neutron, and agreement standard model prediction -0.5706(7). We compare constraints on physics beyond other β-decay measurements, improve value V_{ud} this mirror by factor 4.
We determined the absolute branch of $T=2$ superallowed decay $^{32}\mathrm{Ar}$ by detecting ${\ensuremath{\beta}}^{+}$-delayed protons and \ensuremath{\gamma} decays daughter state. obtain ${b}_{\mathrm{SA}}^{\ensuremath{\beta}}=(22.71\ifmmode\pm\else\textpm\fi{}0.16)%$, which represents first determination a proton to better than 1%. Using this along with previously half-life energy release, we $\mathit{ft}=(1552\ifmmode\pm\else\textpm\fi{}12)$ s for decay. This $\mathit{ft}$ value,...
Masses of the radionuclides $^{32,33}\mathrm{Si}$ and $^{34}\mathrm{P}$ stable nuclides $^{32}\mathrm{S}$ $^{31}\mathrm{P}$ have been measured with Low Energy Beam Ion Trap (LEBIT) Penning trap mass spectrometer. Relative uncertainties as low $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$ achieved. The value $^{32}\mathrm{Si}$ differs from literature by four standard deviations. precise determination employed to test validity quadratic form isobaric multiplet equation (IMME) for...
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...
A high-precision branching ratio measurement for the superallowed beta+ decay of 62Ga was performed at Isotope Separator and Accelerator radioactive ion beam facility. Nineteen gamma rays emitted following were identified, establishing dominant to be (99.861+/-0.011)%. Combined with recent half-life Q-value measurements, this yields a ft value 3075.6+/-1.4 s decay. These results demonstrate feasibility measurements in A>or=62 mass region provide first stringent tests large...
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...
We have measured the angular distribution of recoiling daughter nuclei emitted from Gamow-Teller $\ensuremath{\beta}$ decay spin-polarized $^{80}\mathrm{Rb}$. The asymmetry this vanishes to lowest order in standard model (SM) pure decays, producing an observable very sensitive new interactions. measure non-SM contribution be ${A}_{T}=0.015\ifmmode\pm\else\textpm\fi{}0.029$ (stat) \ifmmode\pm\else\textpm\fi{}0.019 (syst), consistent with SM prediction. constrain higher-order corrections using...
For many fission products, the $\ensuremath{\gamma}$ rays emitted following $\ensuremath{\beta}$ decay provide an easily detectable signature that can be used to identify their quantities and distributions in a sample. As result, $\ensuremath{\gamma}$-ray spectroscopy is often exploited study fission-product yields, provided sufficiently accurate information on intensities available. In cases, uncertainties existing nuclear data are large enough they compromise precision achievable for...
We produced the lowest $T=2$ state in $^{32}\mathrm{S}$ with $^{31}\mathrm{P}$($p,\ensuremath{\gamma}$) reaction and measured energies of deexcitation \ensuremath{\gamma} rays, obtaining an excitation energy $12047.96\ifmmode\pm\else\textpm\fi{}0.28$ keV that disagrees a previous value $12045.0\ifmmode\pm\else\textpm\fi{}0.4$ keV. Our result, together recent measurement $^{32}\mathrm{Ar}$ mass, makes $\text{A}=32$ multiplet most precisely quintet provides easily stringent test isobaric mass...
Precision measurements of free-neutron β decay have been used to precisely constrain our understanding the weak interaction. However, neutron Fierz interference term bn, which is particularly sensitive beyond-standard-model tensor currents at TeV scale, has thus far eluded measurement. Here we report first direct constraints on this term, finding bn=0.067±0.005stat+0.090−0.061sys, consistent with standard model. The uncertainty dominated by absolute energy reconstruction and linearity...
The $\ensuremath{\beta}$ decay of $^{11}\mathrm{Li}$ has been investigated at TRIUMF-ISAC using a high-efficiency array Compton suppressed $\mathrm{HPGe}$ detectors. From line-shape analysis the Doppler-broadened peaks observed in $^{10}\mathrm{Be}$ $\ensuremath{\gamma}$ spectrum, both half-lives states and energies $\ensuremath{\beta}$-delayed neutrons feeding those were obtained. Furthermore, it was possible to determine excitation parent $^{11}\mathrm{B}\mathrm{e}$ with uncertainties...
High-resolution γ-ray spectroscopy is essential to fully exploit the unique, high-quality beams available at next generation of radioactive ion beam facilities such as TRIUMF isotope separator and accelerator (ISAC). The 8π spectrometer, which consists 20 Compton-suppressed HPGe detectors, has recently been reconfigured for a vigorous research programme in weak interaction nuclear structure physics. With addition variety ancillary detectors it become world's most powerful device dedicated...
A precision measurement of the gamma yields following beta decay 32Cl has determined its isobaric analogue branch to be (22.47^{+0.21}_{-0.19})%. Since it is an almost pure Fermi decay, we can also determine amount isospin-symmetry breaking in this superallowed transition. We find a very large value, delta_C=5.3(9)%, agreement with shell-model calculation. This result sets benchmark for isospin-symmetry-breaking calculations and lends support similarly-calculated, yet smaller, corrections...
We demonstrate the transfer of potassium atoms from a vapor-cell type magneto-optical trap (MOT) to second MOT up 75 cm away with use spatially narrow push laser that generates 40-m/s atomic beam. By adding two-dimensional MOT's (atomic funnels) along path generate transverse cooling and compression beam, we can consistently 78±10% atoms.