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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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The atmosphere of Mercury, like that of the moon, is maintained in an extremely tenuous minimum state by weak solar wind accretion and radioactive decay processes, and depleted by strong removal mechanisms. Unlike the moon, it has a high daytime surface temperature that promotes the production of water vapor, which may be the dominant atmospheric constituent derived from solar wind protons.
Astronomical observations of SN1987A, such as the light curve, spectral intensities of lines, the X-ray emissions, etc., constrain the lifetime for the decay of a heavy neutrino 1 MeV less than or equivalent to m sub nu H less than or equal to 50 MeV through nu sub H yields nu sub 1+e(+)+e(-) exceeds 4 x 10 to the 15th exp(-m sub nuH/5MeV) seconds. Otherwise. resulting ionization energy deposits and stronger X-ray emission would have been observed. This coupled with traditional cosmological considerations argues that the lifetime of tau-neutrinos probably exceeds the age of the universe. This in turn would imply the standard cosmological mass bound does apply to nu sub tau, namely m sub nu sub tau less than or equivalent to 100 h squared eV (where h is the Hubble constant in units of 100 km/sec/mpc). The only significant loophole for these latter arguments would be if nu sub tau primarily decays rapidly into particles having very weak interactions.
A ULF pulsation event is discussed on the basis of experimental observations of electric and magnetic field measurements as well as particle measurements from the DE 1 spacecraft. The observations were made near the magnetic equator in a space covering a large range of L shells and magnetic latitudes, and comparisons are made to ground observations. Azimuthal oscillations are observed following gradually decaying long-period compressional waves. Weak interaction between magnetic shells indicates that the source is probably weak, and ground data on magnetic pulsations showed strong signals that did not necessarily correspond to the quasisinusoidal pulsations observed in space. Azimuthal pulsations observed by the spacecraft indicate that there was a plasma density gradient beyond the plasmapause. The ULF pulsations were probably affected by changes in the magnetic field and solar-wind dynamic pressure, and their periods are found to be linked to geomagnetic latitude.
WINDII, the Wind Imaging Interferometer on the Upper Atmosphere Research Satellite, observes winds, temperatures and emission rates in the upper mesosphere and thermosphere. In this paper we report on nighttime observations of the vertical distribution of the O(1S) 557.7 nm emission near the geographic equator for March/April, 1993. The airglow volume emission rate distribution is found to be strongly dependent on local time. Beginning at dusk, an intense airglow emission layer descends from a mean altitude of 95 km, reaching 89 km by midnight after which the emission rapidly decays. Shortly after midnight it reappears weakly at a higher altitude and remains at this level as the emission rate gradually increases towards dawn. This strong local time dependence leads us to conclude that the effect is tidally driven. Comparison with the Forbes (1982a,b) model suggest that total density perturbations and changes in the atomic oxygen mixing ratio may the cause of the changes in emission rate distribution between dusk and midnight. The reappearance of the emission after midnight may be caused by downward winds bringing oxygen-rich air from above.
Dramatic changes have occurred in the mid-to-high-latitude North Atlantic Ocean as evidenced by TOPEX/Poseidon observations of sea surface height (SSH) in the subpolar gyre and the Gulf Stream. Analysis of altimeter data shows that subpolar SSH has increased during the 1990s and the geostrophic velocity derived from altimeter data shows a decline in the gyre circulation. Direct current-meter observations in the boundary current of the Labrador Sea support the trend in the 199Os, and, together with hydrographic data show that in the mid-late 1990s the trend extends deep in the water column. We find that buoyancy forcing over the northern North Atlantic has a dynamic effect consistent with the altimeter data and hydrographic observations: a weak thermohaline forcing and the subsequent decay of the domed structure of the subpolar isopycnals would give rise to the observed anticyclonic circulation trend.
The exponential suppression of macroscopic quantum tunneling (MQT) in the number of elements to be reconfigured is an essential element of broken symmetry phases. This suppression is also a core bottleneck in quantum algorithms, such as traversing an energy landscape in optimization, and adiabatic state preparation more generally. In this work, we demonstrate exponential acceleration of MQT through Floquet engineering with the application of a uniform, high frequency transverse drive field. Using the ferromagnetic phase of the transverse field Ising model in one and two dimensions as a prototypical example, we identify three phenomenological regimes as a function of drive strength. For weak drives, the system exhibits exponentially decaying tunneling rates but robust magnetic order; in the crossover regime at intermediate drive strength, we find polynomial decay of tunnelling alongside vanishing magnetic order; and at very strong drive strengths both the Rabi frequency and time-averaged magnetic order are approximately constant with increasing system size. We support these claims with extensive full wavefunction and tensor network numerical simulations, and theoretical analysis. An experimental test of these results presents a technologically important and novel scientific question accessible on NISQ-era quantum computers.
A direct search for Higgs bosons produced via vector-boson fusion and subsequently decaying into invisible particles is reported. The analysis uses 139 fb -1 of pp collision data at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV recorded by the ATLAS detector at the LHC. The observed numbers of events are found to be in agreement with the background expectation from Standard Model processes. For a scalar Higgs boson with a mass of 125 GeV and a Standard Model production cross section, an observed upper limit of 0.145 is placed on the branching fraction of its decay into invisible particles at 95% confidence level, with an expected limit of 0.103. These results are interpreted in the context of models where the Higgs boson acts as a portal to dark matter, and limits are set on the scattering cross section of weakly interacting massive particles and nucleons. Invisible decays of additional scalar bosons with masses from 50 GeV to 2 TeV are also studied, and the derived upper limits on the cross section times branching fraction decrease with increasing mass from 1.0 pb for a scalar boson mass of 50 GeV to 0.1 pb at a mass of 2 TeV.
We present 3D general-relativistic neutrino-radiation hydrodynamics simulations of two asymmetric binary neutron star mergers producing long-lived neutron stars remnants and spanning a fraction of their cooling time scale. The mergers are characterized by significant tidal disruption with neutron rich material forming a massive disc around the remnant. The latter develops one-armed dynamics that is imprinted in the emitted kilo-Hertz gravitational waves. Angular momentum transport to the disc is initially driven by spiral-density waves and enhanced by turbulent viscosity and neutrino heating on longer timescales. The mass outflows are composed by neutron-rich dynamical ejecta of mass ∼10 −3 –10 −2 M ⊙ followed by a persistent spiral-wave/neutrino-driven wind of ≳ 10 −2 M ⊙ with material spanning a wide range of electron fractions, ∼0.1–0.55. Dynamical ejecta (winds) have fast velocity tails up to ∼0.8 (∼0.4) c. The outflows are further evolved to days timescale using 2D ray-by-ray radiation-hydrodynamics simulations that include an online nuclear network. We find complete r-process yields and identify the production of 56 Ni and the subsequent decay chain to 56 Co and 56 Fe. Synthetic kilonova light curves predict an extended (near-) infrared peak a few days postmerger originating from r-process in the neutron-rich/high-opacity ejecta and UV/optical peaks at a few hours (ten minutes) postmerger originating from weak r-process (free-neutron decay) in the faster ejecta components. Additionally, the fast tail of tidal origin generates kilonova afterglows potentially detectable in radio and X band on a few to ten years time scale. Quantitative effects originating from the tidal disruption merger dynamics are reflected in the multimessenger emissions.
Electron-capture decays of 125 Xe and 127 Xe , and double-electron-capture decays of 124 Xe , are backgrounds in searches for weakly interacting massive particles (WIMPs) conducted by dual-phase xenon time projection chambers such as LUX-ZEPLIN (LZ). These decays produce signals with more light and less charge than equivalent-energy 𝛽 decays and correspondingly overlap more with WIMP signals. We measure three electron-capture charge yields in LZ: the 1.1 keV M-shell, 5.2 keV L-shell, and 33.2 keV K-shell at drift fields of 193 and 96.5 V/cm. The LL double-electron-capture decay of 124 Xe exhibits even more pronounced shifts in charge and light. We provide a first model of double-electron-capture charge yields using the link between ionization density and electron-ion recombination, and identify a need for more accurate calculations. Finally, we discuss the implications of the reduced charge yield of these decays and other interactions creating inner-shell vacancies for future dark matter searches.
Evidence is reported for electroweak (EW) vector boson scattering in the decay channel $\ell\nu$qq of two weak vector bosons WV (V = W or Z), produced in association with two parton jets. The search uses a data set of proton-proton collisions at 13 TeV collected with the CMS detector during 2016-2018 with an integrated luminosity of 138 fb$^{-1}$. Events are selected requiring one lepton (electron or muon), moderate missing transverse momentum, two jets with a large pseudorapidity separation and a large dijet invariant mass, and a signature consistent with the hadronic decay of a W/Z boson. The cross section is computed in a fiducial phase space defined at parton level requiring all parton transverse momenta $p_\mathrm{T}$$\gt$ 10 GeV and at least one pair of outgoing partons with invariant mass $m_\mathrm{qq}$$\gt$ 100 GeV. The measured and expected EW WV production cross sections are 1.90 $^{+0.53}_{-0.46}$ pb and 2.23 $^{+0.08}_{-0.11}$ (scale) $\pm$ 0.05 (PDF) pb, respectively, where PDF is the parton distribution function. The observed EW signal strength is $m_\mathrm{EW}$ = 0.85 $\pm$ 0.12 (stat) $^{+0.19}_{-0.17}$ (syst), corresponding to a signal significance of 4.4 standard deviations with 5.1 expected, and it is measured keeping the quantum chromodynamics (QCD) associated diboson production fixed to the standard model prediction. This is the first evidence of vector boson scattering in the $\ell\nu$qq decay channel at LHC. The simultaneous measurement of the EW and QCD associated diboson production agrees with the standard model prediction.
Two opposite chiralities of Dirac electrons in a two-dimensional (2D) graphene sheet modify the Friedel oscillations strongly: electrostatic potential around an impurity in graphene decays much faster than in 2D electron gas. At distances $\textit{r}$ much larger than the de Broglie wavelength, it decays as 1/$r^3$. Here we show that a weak uniform magnetic field affects the Friedel oscillations in an anomalous way. It creates a field-dependent contribution which is dominant in a parametrically large spatial interval $p^{–1}_0 ≲ r ≲ k_Fl^2$, where $\textit{l}$ is the magnetic length, $k_F$ is Fermi momentum, and $p^{–1}_0 = (k_Fl)^{4/3} /k_F$. Moreover, in this interval, the field-dependent oscillations do not decay with distance. The effect originates from a spin-dependent magnetic phase accumulated by the electron propagator. Further, the obtained phase may give rise to novel interaction effects in transport and thermodynamic characteristics of graphene and graphene-based heterostructures.
We analyze the recoil corrections in superallowed beta decays of T = 1, J P = 0 + nuclei by fixing the mean square charged weak radius model independently using the data of multiple charge radii across the nuclear isotriplet. By comparing to model estimations, we argue that the existing theory uncertainty in the statistical rate function f might have been substantially underestimated. Here, we discuss the implications of our proposed strategy for precision tests of the standard model, including a potential alleviation of the first-row CKM unitarity deficit, and motivate new experiments for charge radii measurements.
Axionlike particles (ALPs) are well-motivated examples of light, weakly coupled particles in theories beyond the Standard Model. In this work, we study long-lived ALPs coupled exclusively to leptons in the mass range between 2𝑚 𝑒 and 𝑚 𝜏 − 𝑚 𝑒 . For anarchic flavor structure the leptophilic ALP production in tau decays or from ALP-tau bremsstrahlung is enhanced thanks to derivative couplings of the ALP and can surpass production from electron and muon channels, especially for ALPs heavier than 𝑚 𝜇 . Using past data from high-energy fixed-target experiments such as CHARM and BEBC we place new constraints on the ALP decay constant 𝑓 𝑎 , reaching scales as high as 𝒪(10 8 ) GeV in lepton-flavor-violating channels and 𝑓 𝑎 ∼ 𝒪(10 2 ) GeV in lepton-flavor-conserving ones. We also present projections for the event-rate sensitivity of current and future detectors to ALPs produced at the Fermilab Main Injector, the CERN SPS, and in the forward direction of the LHC. We show that SHiP will be sensitive to 𝑓 𝑎 values that are over an order of magnitude above the existing constraints.
The Nab apparatus at the Fundamental Neutron Physics Beamline at the Spallation Neutron Source was designed to measure key observations in neutron beta decay, test the Standard Model's description of the weak interaction, and search for new physics. This data was collected using the Nab apparatus and are presented in the article "First Full Dalitz Plot Measurement in Neutron β-Decay using the Nab Spectrometer and Implications for New Physics." This data publication includes CSV (comma-separated values) files which are used to generate Figures 3 - 11 in the linked journal article.
We present strategies for the Mu3e experiment to search for light, weakly coupled particles produced in rare muon decays, focusing on displaced e+e− decays within the hollow target. In most scenarios the backgrounds can be fully suppressed with a suitable set of cuts. We furthermore quantify the interplay between displaced and prompt searches at Mu3e and existing constraints, showing how Mu3e has a unique opportunity to probe unexplored parameter space.
Abstract We discuss QED radiative corrections to contact operators coupling two heavy fields and one light field. These operators appear ubiquitously in weak interactions with nuclei such as beta decay and neutrino nucleus scattering. New eikonal identities are derived in the static limit (i.e., neglecting nuclear recoil) that allow for manifest power counting of enhancements proportional to the charge of the nucleus. We apply these new identities to nuclear beta decays and find that the “independent particle model” used by Jaus, Rasche, Sirlin & Zucchini is closely related, though not identical, to a model independent effective field theorcalculation.
Strong and weak interactions of elementary particles and particle decay