L. J. Broussard
A5000656251- Atomic and Subatomic Physics Research
- Nuclear Physics and Applications
- Quantum, superfluid, helium dynamics
- Dark Matter and Cosmic Phenomena
- Radiation Detection and Scintillator Technologies
- Particle physics theoretical and experimental studies
- Neutrino Physics Research
- Cold Atom Physics and Bose-Einstein Condensates
- Particle Detector Development and Performance
- Nuclear physics research studies
- Radioactive Decay and Measurement Techniques
- Computational Physics and Python Applications
- Nuclear reactor physics and engineering
- Nuclear Materials and Properties
- Quantum Chromodynamics and Particle Interactions
- Particle accelerators and beam dynamics
- Fusion materials and technologies
- Atmospheric Ozone and Climate
- Cosmology and Gravitation Theories
- Radiation Therapy and Dosimetry
- Particle Accelerators and Free-Electron Lasers
- Advanced NMR Techniques and Applications
- Glass properties and applications
- Spectroscopy and Chemometric Analyses
- Polymer Nanocomposites and Properties
Oak Ridge National Laboratory
2016-2024
European Spallation Source
2023
Los Alamos National Laboratory
2013-2021
Duke University
2008-2019
Triangle Universities Nuclear Laboratory
2009-2019
North Carolina State University
2013
Tulane University
2004
University of Louisiana at Lafayette
2001
Università Cattolica del Sacro Cuore
1985
We report an improved measurement of the free neutron lifetime τ_{n} using UCNτ apparatus at Los Alamos Neutron Science Center. count a total approximately 38×10^{6} surviving ultracold neutrons (UCNs) after storing in UCNτ's magnetogravitational trap over two data acquisition campaigns 2017 and 2018. extract from three blinded, independent analyses by both pairing long short storage time runs to find set replicate measurements performing global likelihood fit all while self-consistently...
The precise value of the mean neutron lifetime, $\tau_n$, plays an important role in nuclear and particle physics cosmology. It is a key input for predicting ratio protons to helium atoms primordial universe used search new beyond Standard Model physics. There 3.9 standard deviation discrepancy between $\tau_n$ measured by counting decay rate free neutrons beam (887.7 $\pm$ 2.2 s) surviving ultracold stored different storage times material trap (878.5$\pm$0.8 s). experiment described here...
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.
The violation of Baryon Number, $\mathcal{B}$, is an essential ingredient for the preferential creation matter over antimatter needed to account observed baryon asymmetry in universe. However, such a process has yet be experimentally observed. HIBEAM/NNBAR %experiment program proposed two-stage experiment at European Spallation Source (ESS) search number violation. will include high-sensitivity searches processes that violate by one or two units: free neutron-antineutron oscillation...
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 $λ\equiv g_A/g_V -1.2756(30)$.
Fornal and Grinstein recently proposed that the discrepancy between two different methods of neutron lifetime measurements, beam bottle methods, can be explained by a previously unobserved dark matter decay mode, $n\ensuremath{\rightarrow}X+\ensuremath{\gamma}$. We perform search for this mode over allowed range energies monoenergetic $\ensuremath{\gamma}$ ray $X$ to matter. A Compton-suppressed high-purity germanium detector is used identify rays from in nickel-phosphorous-coated...
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 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...
An unexplained >4σ discrepancy persists between "beam" and "bottle" measurements of the neutron lifetime. A new model proposed that conversions neutrons n into mirror n^{'}, part a dark sector, can increase apparent lifetime by 1% via small mass splitting Δm n^{'} inside 4.6 T magnetic field National Institute Standards Technology Beam Lifetime experiment. search for in 6.6 was performed at Spallation Neutron Source which excludes this explanation discrepancy.
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...
A precise value for the neutron lifetime (about 880 s) is needed nuclear astrophysics predictions of Big-Bang nucleosynthesis and solar neutrino production, as well in precision searches new physics beyond Standard Model. This work reports on a type magnetic trap that has potential to resolve present 4-sigma inconsistency measurements lifetime, suggests next generation with less than one second uncertainty possible.
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...
In this paper, we describe a new method for measuring surviving neutrons in neutron lifetime measurements using bottled ultracold (UCN), which provides better characterization of systematic uncertainties and enables higher precision than previous measurement techniques. An active detector that can be lowered into the trap has been used to measure distribution as function height influence marginally trapped UCN on measurement. addition, have demonstrated phase-space evolution its effect
Neutron beta decay is one of the most fundamental processes in nuclear physics and provides sensitive means to uncover details weak interaction. can evaluate ratio axial-vector vector coupling constants standard model, λ = g A / V , through multiple correlations. The Nab experiment will carry out measurements electron-neutrino correlation parameter a with precision δ 10 −3 Fierz interference term b 3 × unpolarized free neutron decay. These results, along more precise measurement lifetime,...
The $\frac{1}{2}^+ \rightarrow \frac{1}{2}^+$ superallowed mixed mirror decay of $^{19}$Ne to $^{19}$F is excellently suited for high precision studies the weak interaction. However, there some disagreement on value half-life. In a new measurement we have determined this quantity be $T_{1/2}$ = $17.2832 \pm 0.0051_{(stat)}$ $\pm 0.0066_{(sys)}$ s, which differs from previous world average by 3 standard deviations. impact limits physics beyond model such as presence tensor currents discussed.
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...
A key aim of the HighNESS project for European Spallation Source is to enable cutting-edge particle physics experiments. This volume presents a conceptual design report NNBAR experiment. would exploit new cold lower moderator make first search in over thirty years free neutrons converting anti-neutrons. The observation such baryon-number-violating signature be fundamental significance and tackle open questions modern physics, including origin matter-antimatter asymmetry. shows beamline,...