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Results for “WEAK INTERACTIONS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

A weak interaction study of the viscous flow about oscillating airfoils

An incompressible inviscid and a viscous flow calculation procedure is developed by assuming the viscous correction to the inviscid flow pressure distribution is small (weak interaction) to predict the flow about airfoils oscillating in pitch and heave. The calculations made in the investigation predict the detailed viscous flow regions including transition and separation phenomena and provide a detailed analysis of leading edge separation, transition, and reattachment. Results from the calculation show the leading edge viscous flow field to be quasi-steady although the imposed inviscid pressure distribution shows significant unsteady effects. Although unable to predict the flow field about a stalled airfoil, the indications are that the present procedure can indicate the onset of catastrophic flow separation.

Shamroth, S. J.↗
DOE OSTI2021

An Indirect Search for Weakly Interacting Massive Particles in the Sun Using Upward-going Muons in NOvA

I present the first Dark Matter search results using the full data set collected with the upward-going muon trigger in NOvA. Weakly Interactive Massive Particles (WIMPs) are a theoretical non-baryonic form of Dark Matter. The nature of Dark Matter is one of the most exciting open questions in modern physics. Though its existence can be inferred by astrophysical evidence, its properties are not yet understood. If we assume that Dark Matter particles can produce Standard Model particles through their interactions, an indirect search can help shed light on this mystery.The NOvA collaboration has built a 14 kton, fine-grained, low-Z, total absorption tracking calorimeter at an off-axis angle to the NuMI neutrino beam. Even though the detector is optimized to observe electron neutrino appearance from a muon neutrino beam, it has a unique potential for more exotic searches given its excellent granularity and energy resolution and relatively low-energy neutrino thresholds. In fact, with an efficient upward-going muon trigger and sufficient background suppression offline, NOvA is capable of a competitive indirect Dark Matter search for low-mass WIMPs.The idea of the upward-going muon trigger is first to select high-quality muon tracks, then use the timing information of all of the hits of each track to estimate directionality. In this way, the background flux is suppressed by more than a factor of 10^5 at trigger level to a rate of approximately 1 Hz. To further optimize this search, we use only upward-going muons that point to the Sun, so our search occurs at night when the Sun is on the other side of the Earth. This strategy also allows us to use the time when the Sun is above the horizon as a control region to estimate the background. Ultimately, implementation of a cut based and maximum likelihood analysis provides a powerful tool for rejecting background and selecting a sample of neutrino-induced upward-going muons. The overall background rejection power achieved by the analysis is substantial and impressive. Starting with approximately 150,000 events per second, we reduced it to 40 events per year. Since no statistically significant excess was found, a 90\% C.L. upper limit on the expected muon flux of upward-going muons has been set using the upper limit on the number of events given the number of observed events in the signal region. Lastly, by assuming the theory behind the upward-going muon flux, a limit on the WIMP-nucleon spin-dependent cross-section in the Sun was estimated. Although the limits on the spin-dependent cross-section do not appear to be competitive with previous indirect Dark Matter searches, the upward-going muon flux limits are promising. The upward-going muon flux limits could extend these results to a broader class of models that are not specific to the dark matter theory but produce upward-going muons, leading to competitive results.

Principato, Cristiana↗
DOE OSTI2014

Electrokinetic detection for X-ray spectra of weakly interacting liquids: n-decane and n-nonane

The introduction of liquid microjets into soft X-ray absorption spectroscopy enabled the windowless study of liquids by this powerful atom-selective high vacuum methodology. However, weakly interacting liquids produce large vapor backgrounds that strongly perturb the liquid signal. Consequently, solvents (e.g., hydrocarbons, ethers, ketones, etc.) and solutions of central importance in chemistry and biology have been inaccessible by this technology. Here we describe a new detection method, upstream detection, which greatly reduces the vapor phase contribution to the X-ray absorption signal while retaining important advantages of liquid microjet sample introduction (e.g., minimal radiation damage). The effectiveness of the upstream detection method is demonstrated in this first study of room temperature liquid hydrocarbons: n-nonane and n-decane. Good agreement with first principles’ calculations indicates that the eXcited electron and Core Hole theory adequately describes the subtle interactions in these liquids that perturb the electronic structure of the unoccupied states probed in core-level experiments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

A Search for Light Weakly-Interacting Massive Particles with SuperCDMS and Applications to Neutrino Physics

Cosmological and astrophysical evidence indicates that 85% of the matter content of the universe is in the form of non-baryonic dark matter. A large number of experiments are currently undertaking searches for weakly-interacting massive particles (WIMPs), the leading class of particle candidates for dark matter. This thesis describes the results of such a search with the SuperCDMS experiment, which uses Ge detectors cooled to 50 mK to detect ionization and phonons produced by particle interactions. We perform a blind analysis of 577 kg d of exposure on 7 detectors targeting WIMPs with masses < 30GeV/$c^{2}$, where anomalous results have been reported by previous experiments. No significant excess is observed and we set an upper limit on the spin-independent WIMP-nucleon cross section of 1.2 x 10$^{-42}$ cm2 at 8 GeV/$c^{2}$ We also set constraints on dark matter interactions independent of the dark matter halo physics, as well as on annual modulation of a dark matter signal. Cryogenic detectors similar to SuperCDMS also have potential applications in neutrino physics. We study several configurations in which dark matter detectors could be used with an intense neutrino source to detect an unmeasured Standard Model process called coherent neutrino scattering. This process may be useful, for example, as a calibration for next-generation dark matter detectors, and for constraining eV-scale sterile neutrinos. In addition, small cryogenic X-ray detectors on sounding rockets with large fields-of-view have the unique ability to constrain sterile neutrino dark matter. We set limits on sterile neutrino dark matter using an observation by the XQC instrument, and discuss prospects for a future observation of the galactic center using the Micro-X instrument.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Weakly-interacting massive particles in non-supersymmetric SO(10) grand unified models

Here, non-supersymmetric SO(10) grand unified theories provide a framework in which the stability of dark matter is explained while gauge coupling unification is realized. In this work, we systematically study this possibility by classifying weakly interacting dark matter candidates in terms of their quantum numbers of SU(2) L Ⓧ U(1) Y , B – L, and SU(2) R . We consider both scalar and fermion candidates. We show that the requirement of a sufficiently high unification scale to ensure a proton lifetime compatible with experimental constraints plays a strong role in selecting viable candidates. Among the scalar candidates originating from either a 16 or 144 of SO(10), only SU(2) L singlets with zero hypercharge or doublets with Y = 1/2 satisfy all constraints for SU(4) C Ⓧ SU(2) L Ⓧ SU(2) R and SU(3) C Ⓧ SU(2) L Ⓧ SU(2) R Ⓧ U(1) B–L intermediate scale gauge groups. Among fermion triplets with zero hypercharge, only a triplet in the 45 with intermediate group SU(4) C Ⓧ SU(2) L Ⓧ SU(2) R leads to solutions with M GUT > M int and a long proton lifetime. We find three models with weak doublets and Y = 1/2 as dark matter candidates for the SU(4) C Ⓧ SU(2) L Ⓧ SU(2) R and SU(4) C Ⓧ SU(2) L Ⓧ U(1) R intermediate scale gauge groups assuming a minimal Higgs content. We also discuss how these models may be tested at accelerators and in dark matter detection experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

A Search For Weakly Interacting Massive Particles Utilizing A Profile Likelihood Ratio Technique With The Super CDMS Soudan Experiment

Dark matter accounts for ~26.8% of the universe’s mass and ~85% of the matter of the universe. The majority of dark matter is in the form of non-baryonic dark matter. Among all the dark matter particle candidates, the Weakly Interacting Massive Particle (WIMP) is considered the most promising. Tens of experiments around the world are under the searches of WIMPs. The Super Cryogenic Dark Matter Search (SuperCDMS) is one of the leading direct dark matter search experiments. Its latest experiment was located in the Soudan Underground Laboratory in northern Minnesota. By placing its germanium (Ge) detectors deep underground, it aimed at performing a rare-event search in the case that a WIMP would collide with a Ge nucleus and leave a Ge nuclear recoil signal in the detectors. These Ge detectors were operated at a temperature of ~50 mK to reduce the noise from disturbing the ionization and phonon signal collections. A high mass WIMP search analysis is performed on the recent collected data sets at Soudan. It aims at exploring WIMPs with masses from the order of 10 GeV/c 2 and above. With a raw exposure of 1657.54 kg-days, an exclusion limit is set on the spin-independent WIMP-nucleon cross section at 1.32 ×10 -44 cm 2 for a 75 GeV/c2 WIMP at a 90% confidence level by the profile likelihood ratio technique. Neutrons are the most dangerous background in a direct dark matter search experiment. The nuclear recoil signal that a neutron produces in a Ge detector is indistinguishable from vii that a WIMP produces. Protection against them is one of the key aspects for the next generation of SuperCDMS experiment at SNOLAB. An active neutron veto system was proposed to be implemented in this future experiment to make it more robust from neutrons. The feasibility of both the plastic and liquid neutron veto systems was studied.

Qiu, Hang↗
DOE OSTI2022

Eigenstate thermalization and disappearance of quantum many-body scar states in weakly interacting fermion systems

The recent discovery of quantum many-body scar states has revealed the possibility of having states with low entanglement that violate the eigenstate thermalization hypothesis in nonintegrable systems. Eigenstates with low entanglement entropy are rare but naturally exist in the integrable system of free fermions. Here, we demonstrate analytically that these atypical states would be always eliminated when an arbitrary weak interaction is introduced between the fermions. In particular, we show that the probability of having a many-body scar state with entanglement entropy satisfying a sub-volume scaling law decreases double exponentially as the system size. Furthermore, our results provide a quantitative argument for the disappearance of scar states in interacting fermion systems.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2003

A Macroscopic Realization of the Weak Interaction

A.J.Leggett suggested in 1977 that a permanent electric dipole moment due to the parity-nonconserving electron-nucleon interaction, even though it is extremely small, could be measured in the superfluid He-3 B because the moment should be proportional to the size of the sample in this system. If this moment is observed, it will be the first example of a macroscopic realization of the weak interaction. In our planned experiments, a high electric field of up to 6 kV/cm is applied between two parallel electrodes in the He-3 sample. We expect to observe the NMR frequency of the lowest-lying spin-wave mode trapped by the liquid crystal-like texture of the B phase rotation axis in our geometry. The interaction of the electric field and the macroscopic permanent electric dipole moment, which is oriented along the rotation axis, will cause a small change in the texture and hence a small increase in the frequency of the spin wave mode. Besides the basic ideas, we present the purpose and the design of our first cell that is under construction.

Nishimori, Arito↗
DOE OSTI2015

Exact kinetic energy enables accurate evaluation of weak interactions by the FDE-vdW method

The correlation energy of interaction is an elusive and sought-after interaction between molecular systems. By partitioning the response function of the system into subsystem contributions, the Frozen Density Embedding (FDE)-vdW method provides a computationally amenable nonlocal correlation functional based on the adiabatic connection fluctuation dissipation theorem applied to subsystem density functional theory. In reproducing potential energy surfaces of weakly interacting dimers, we show that FDE-vdW, either employing semilocal or exact nonadditive kinetic energy functionals, is in quantitative agreement with high-accuracy coupled cluster calculations (overall mean unsigned error of 0.5 kcal/mol). When employing the exact kinetic energy (which we term the Kohn-Sham (KS)-vdW method), the binding energies are generally closer to the benchmark, and the energy surfaces are also smoother.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1994

Search for important weak interaction nuclei in presupernova evolution

A search is made for the most important electron captures and beta-decays after core silicon burning in massive stars. A nuclear statistical equilibrium code is used to compute isotopic abundances. Electron capture and beta-decay rates are estimated for the 150 most abundant isotopes in a simplified fashion which generally includes the strongest transitions. These estimates are made for nuclei in the fp-shell and use techniques similar to Fuller, Fowler, & Newman (1982a), and are compared to them. The general behavior of the rate of change of Y(sub e) is examined. These methods are then used to follow a typical stellar trajectory, seeking the most important weak interactions during the formation of the iron core. Ranked lists of nuclei are given, to prioritize more detailed studies on individual nuclei. Beta-decays are found to ben an important modification to the evolution below the rate of change of Y(sub e) approx. = 0.46 as the core approaches a state of dynamic equilibrium between electron captures and beta-decays.

Aufderheide, Maurice B.↗
DOE OSTI2019

Quantum optimal control of multiple weakly interacting molecular rotors in the time-dependent Hartree approximation

In this work we perform quantum optimal control simulations, based on the Time-Dependent Hartree (TDH) approximation, for systems of three to five dipole-dipole coupled OCS rotors. A control electric field is used to steer all of the individual rotors, arranged in chains and regular polygons in a plane, toward either identical or unique objectives. The goal is to explore the utility of the TDH approximation to model the field-induced dynamics of multiple interacting rotors in the weak dipole-dipole coupling regime. A stochastic hill climbing approach is employed to seek an optimal control field that achieves the desired objectives at a specified target time. We first show that multiple rotors in chain and polygon geometries can be identically oriented in the same direction; these cases do not significantly depend on the presence of the dipole-dipole interaction. Additionally, in particular geometrical arrangements, we demonstrate that individual rotors can be uniquely manipulated toward different objectives with the same field. Specifically, it is shown that for a three rotor chain, the two end rotors can be identically oriented in a specific direction while keeping the middle rotor in its ground state, and for an equilateral triangle, two rotors can be identically oriented in a specific direction while the third rotor is oriented in the opposite direction. These multirotor unique objective cases exploit the shape of the field in coordination with dipole-dipole coupling between the rotors. Comparisons to numerically exact calculations, utilizing the TDH-determined fields, are given for all optimal control studies involving systems of three rotors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Spectral function in electro-weak interactions and its impact on neutrino oscillation experiments

Neutrino oscillation experiments have entered the high-precision era in the last few years. The oscillation parameters, as a measure of the neutrino properties, are extracted from the energy-dependent oscillation probability function. Different types of nuclear dynamics deeply influence the determination of neutrino energies in neutrino oscillation experiments. As a consequence, a comprehensive understanding of various nuclear dynamics interprets the scenario behind the neutrino interaction with nucleus and nuclei. The initial ground-state structure of the target nucleus is categorized in one typical nuclear dynamics, and its realistic description is generally referred as the spectral function (SF). Implementing the SF for each target nucleus into the GENIE neutrino event generator is the preliminary step necessary to obtain a reliable determination of the kinematics of all detectable final-products from neutrino interactions. At the intermedium-range of neutrino energies (∼ 1 GeV), the kinematic energy reconstruction is the vastly used approach and consists in identifying final-products as coming from the charged-current quasi-elastic-like (CCQE-like) neutrino interactions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

A new equation of state with light nuclei and their weak interactions in core-collapse supernova simulations

We perform numerical experiments to investigate the influence of inelastic neutrino reactions with light nuclei on the standing accretion shock instability. The time evolutions of shock waves are calculated with a simple light-bulb approximation for the neutrino transport and a multi-nuclei equation of state. The neutrino absorptions and inelastic interactions with deuterons, tritons, helions and alpha particles are taken into account in the hydrodynamical simulations in addition to the ordinary charged-current interactions with nucleons. Axial symmetry is assumed but no equatorial symmetry is imposed. We show that the heating rates of deuterons reach as high as ∼ 10% of those of nucleons around the bottom of the gain region. On the other hands, alpha particles heat the matter near the shock wave, which is important when the shock wave expands and density and temperature of matter become low. It is also found that the models with heating by light nuclei have different evolutions from those without it in non-linear evolution phase. The matter in the gain region has various densities and temperatures and there appear regions that are locally rich in deuterons and alpha particles. These results indicate that the inelastic reactions of light nuclei, especially deuterons, should be incorporated in the simulations of core-collapse supernovae.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Weak interactions in Graphane/BN systems under static electric fields—A periodic ab-initio study

Ab-initio calculations via periodic Hartree-Fock (HF) and local second-order Møller-Plesset perturbation theory (LMP2) are used to investigate the adsorption properties of combined Graphane/boron nitride systems and their response to static electric fields. It is shown how the latter can be used to alter both structural as well as electronic properties of these systems.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Studies of the weak interaction in atomic systems: towards measurements of atomic parity non-conservation in francium

Abstract Tests of the standard model of particle physics should be carried out over the widest possible range of energies. Here we present our plans and progress for an atomic parity non-conservation experiment using the heaviest alkali, francium ( Z = 87), which has no stable isotope. Low-energy tests of this kind have sensitivity complementary to higher energy searches, e.g. at the large hadron collider.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2013

Weak interaction between germanene and GaAs(0001) by H intercalation: A route to exfoliation

Epitaxial germanene on a semiconducting GaAs(0001) substrate is studied by ab initio calculations. The germanene-substrate interaction is found to be strong for direct contact but can be substantially reduced by H intercalation at the interface. Our results indicate that it is energetically possible to take the germanene off the GaAs(0001) substrate. While mounted on the substrate, the electronic structure shows a distinct Dirac cone shift above the Fermi energy with a splitting of 175 meV. On the other hand, we find for a free standing sheet a band gap of 24 meV, which is due to the intrinsic spin orbit coupling.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Wavefunction collapse through backaction of counting weakly interacting photons

We apply the formalism of quantum measurement theory to the idealized measurement of the position of a particle with an optical interferometer, finding that the backaction of counting entangled photons systematically collapses the particle’s wavefunction toward a narrow Gaussian wavepacket at the location x{sub est} determined by the measurement without appeal to environmental decoherence or other spontaneous collapse mechanism. Further, the variance in the particle’s position, as calculated from the post-measurement wavefunction, agrees precisely with shot-noise limited uncertainty of the measured x{sub est}. Both the identification of the absolute square of the particle’s initial wavefunction as the probability density for x{sub est} and the de Broglie hypothesis emerge as consequences of interpreting the intensity of the optical field as proportional to the probability of detecting a photon. Linear momentum information that is encoded in the particle’s initial wavefunction survives the measurement, and the pre-measurement expectation values are preserved in the ensemble average.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Higgs gravitational interaction, weak boson scattering, and Higgs inflation in Jordan and Einstein frames

We study gravitational interaction of Higgs boson through the unique dimension-4 operator ξH{sup †}HR, with H the Higgs doublet and R the Ricci scalar curvature. We analyze the effect of this dimensionless nonminimal coupling ξ on weak gauge boson scattering in both Jordan and Einstein frames. We explicitly establish the longitudinal-Goldstone equivalence theorem with nonzero ξ coupling in both frames, and analyze the unitarity constraints. We study the ξ-induced weak boson scattering cross sections at O(1−30) TeV scales, and propose to probe the Higgs-gravity coupling via weak boson scattering experiments at the LHC (14 TeV) and the next generation pp colliders (50-100 TeV). We further extend our study to Higgs inflation, and quantitatively derive the perturbative unitarity bounds via coupled channel analysis, under large field background at the inflation scale. We analyze the unitarity constraints on the parameter space in both the conventional Higgs inflation and the improved models in light of the recent BICEP2 data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗