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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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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Search for dark matter produced in association with a single top quark and an energetic W boson in $\sqrt{s}=$ 13 TeV $pp$ collisions with the ATLAS detector

This paper presents a search for dark matter, $χ$, using events with a single top quark and an energetic W boson. The analysis is based on proton–proton collision data collected with the ATLAS experiment at $\sqrt{s}=$ 13 TeV during LHC Run 2 (2015–2018), corresponding to an integrated luminosity of 139 fb -1 . The search considers final states with zero or one charged lepton (electron or muon), at least one $b$-jet and large missing transverse momentum. In addition, a result from a previous search considering two-charged-lepton final states is included in the interpretation of the results. The data are found to be in good agreement with the Standard Model predictions and the results are interpreted in terms of 95% confidence-level exclusion limits in the context of a class of dark matter models involving an extended two Higgs-doublet sector together with a pseudoscalar mediator particle. The search is particularly sensitive to on-shell pro duction of the charged Higgs boson state, $H$ ± , arising from the two-Higgs-doublet mixing, and its semi-invisible decays via the mediator particle, $a$: $H$ ± → $W$ ± $a$(→ $χ$ $χ$). Signal models with $H$ ± masses up to 1.5 TeV and a masses up to 350 GeV are excluded assuming a tan $β$ value of 1. For masses of a of 150 (250) GeV, tan $β$ values up to 2 are excluded for $H$ ± masses between 200 (400) GeV and 1.5 TeV. Signals with tan $β$ values between 20 and 30 are excluded for $H$ ± masses between 500 and 800 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

R -parity violation axiogenesis

We show that the rotation of the QCD axion field, aided by B–L violation from supersymmetric R-parity violating couplings, can yield the observed baryon abundance. Strong sphaleron processes transfer the angular momentum of the axion field into a quark chiral asymmetry, which R-parity violating couplings convert to the baryon asymmetry of the Universe. We focus on the case of dimensionless R-parity violating couplings with textures motivated by grand unified theories and comment on more general scenarios. The axion decay constant and mass spectrum of supersymmetric particles are constrained by Big Bang nucleosynthesis, proton decay from the R-parity violation, and successful thermalization of the Peccei-Quinn symmetry breaking field. Axion dark matter may be produced by the axion rotation via the kinetic misalignment mechanism for axion decay constants below 10 10 GeV, or by the conventional misalignment mechanism for 10 11-12 GeV. The viable parameter region can be probed by proton decay and axion searches. This scenario may also have connections with collider experiments, including searches for long-lived particles, and observations of gravitational waves.

Beyond Standard Model↗
DOE OSTI2021

Search for dark photons in Higgs boson production via vector boson fusion in proton-proton collisions at $ \sqrt{s} $ = 13 TeV

A search is presented for a Higgs boson that is produced via vector boson fusion and that decays to an undetected particle and an isolated photon. The search is performed by the CMS collaboration at the LHC, using a data set corresponding to an integrated luminosity of 130 fb$^{−1}$, recorded at a center-of-mass energy of 13 TeV in 2016–2018. No significant excess of events above the expectation from the standard model background is found. The results are interpreted in the context of a theoretical model in which the undetected particle is a massless dark photon. An upper limit is set on the product of the cross section for production via vector boson fusion and the branching fraction for such a Higgs boson decay, as a function of the Higgs boson mass. For a Higgs boson mass of 125 GeV, assuming the standard model production rates, the observed (expected) 95% confidence level upper limit on the branching fraction is 3.5 (2.8)%. This is the first search for such decays in the vector boson fusion channel. Combination with a previous search for Higgs bosons produced in association with a Z boson results in an observed (expected) upper limit on the branching fraction of 2.9 (2.1)% at 95% confidence level.[graphic not available: see fulltext]

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Heavy neutral leptons at the Electron-Ion Collider

The future Electron-Ion Collider (EIC) at Brookhaven National Laboratory, along with its primary capacity to elucidate the nuclear structure, will offer new opportunities to probe physics beyond the Standard Model coupled to the electroweak sector. Among the best motivated examples of such new physics are new heavy neutral leptons (HNLs), which are likely to play a key role in neutrino mass generation and lepton number violation. We study the capability of the EIC to search for HNLs, which can be produced in electron- proton collisions through charged current interactions as a consequence of their mixing with light neutrinos. We find that, with the EIC design energy and integrated luminosity, one is able to probe HNLs in the mass range of 1 – 100 GeV with mixing angles down to the order of 10 -4 - 10 -3 through the prompt decay signatures, and in the mass range of 1 10 GeV with |U e | 2 ~ 10 -6 - 10 -4 via the displaced decay signatures. We also consider the invisible mode where an HNL is undetected or decaying to dark sector particles. One could potentially probe heavy HNLs for mixing angles in the window 10 -3 - 10 -2 , provided SM background systematics can be brought under control. These searches are complementary to other probes of HNLs, such as neutrino-less double-β decay, meson decay, fixed-target, and high-energy collider experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Tripling down on the W boson mass

A new precision measurement of the W boson mass has been announced by the CDF collaboration, which strongly deviates from the Standard Model prediction. In this article, we study the implications of this measurement on the parameter space of the SU(2) L triplet extension (with hypercharge Y=1) of the Standard Model Higgs sector, focusing on a limit where the new triplet is approximate Z 2 -odd while the SM is Z 2 -even. We study the compatibility of the triplet spectrum preferred by the W boson mass measured by the CDF-II experiment with other electroweak precision observables and Higgs precision data. We comprehensively consider the signals of new Higgs states at the LHC and highlighted the promising search channels. In addition, we also investigate the cosmological implications of the case in which the lightest new Higgs particle is either late decaying or cosmologically stable.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Observation of the $γγ → ττ$ Process in $\mathrm{Pb + Pb}$ Collisions and Constraints on the $\tau$-Lepton Anomalous Magnetic Moment with the ATLAS Detector

This Letter reports the observation of τ-lepton pair production in ultraperipheral lead-lead collisions, Pb+Pb→Pb(γγ→ττ)Pb, and constraints on the τ-lepton anomalous magnetic moment, a τ . The dataset corresponds to an integrated luminosity of 1.44 nb -1 of LHC Pb+Pb collisions at $\sqrt{s_{NN}}$ =5.02 TeV recorded by the ATLAS experiment in 2018. Selected events contain one muon from a τ-lepton decay, an electron or charged-particle track(s) from the other τ-lepton decay, little additional central-detector activity, and no forward neutrons. The γγ→ττ process is observed in Pb+Pb collisions with a significance exceeding 5 standard deviations, and a signal strength of μ ττ =1.03$^{+0.06}_{-0.05}$ assuming the Standard Model value for a τ . To measure a τ , a template fit to the muon transverse-momentum distribution from τ-lepton candidates is performed, using a dimuon (γγ→μμ) control sample to constrain systematic uncertainties. The observed 95% confidence-level interval for aτ is -0.057 < a τ < 0.024.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Constraints on MeV dark matter and primordial black holes: Inverse Compton signals at the SKA

Here we investigate the possibilities for probing MeV dark matter (DM) particles and primordial black holes (PBHs) (for masses ~ 10 15 –10 17 g) at the upcoming radio telescope SKA, using photon signals from the Inverse Compton (IC) effect within a galactic halo. Pair-annihilation or decay of MeV DM particles (into e + e - pairs) or Hawking radiation from a population of PBHs generates mildly relativistic e ± which can lead to radio signals through the IC scattering on low energy cosmic microwave background (CMB) photons. We study the ability of SKA to detect such signals coming from nearby ultra-faint dwarf galaxies Segue I and Ursa Major II as well as the globular cluster ω-cen and the Coma cluster. We find that with ~ 100 hours of observation, the SKA improves the Planck constraints on the DM annihilation/decay rate and the PBH abundance for masses in the range ~ 1 to few tens of MeV and above 10 15 to 10 17 g, respectively. Importantly, the SKA limits are independent of the assumed magnetic fields within the galaxies. Previously allowed regions of diffusion parameters of MeV electrons inside a dwarf galaxy that give rise to observable signals at the SKA are also excluded. For objects like dwarf galaxies, predicted SKA constraints depend on both the DM and diffusion parameters. Independent observations in different frequency bands, e.g., radio and γ-ray frequencies, may break this degeneracy and thus enable one to constrain the combined parameter space of DM and diffusion. However, the constraints are independent of diffusion parameters for galaxy clusters such as Coma.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1973

Time variations of magnetospheric intensities of outer zone protons, alpha particles and ions (Z greater than or equal to 2)

A comprehensive study of the temporal behavior of trapped protons, alpha particles and ions (Z 2) in outer zone of the earth's magnetosphere has been made. These observations were made by the Injun V satellite during the first 21 months of operation, August 1968 to May 1970. Rapid increases in the observed number of particles followed by slower exponential decay characterize the data. Comparisons are made with the temporal behavior of interplanetary particles of the same energy observed by Explorer 35. Increases in the trapped fluxes generally correspond to enhanced interplanetary activity. The energy spectra of protons and alpha particles at L = 3 have similar shapes when compared on an energy per charge basis while the respective polar cap spectra have similar shape on an energy per nucleon basis. Apparent inward trans-L motion of energetic protons is observed. These particles are diffused inward by a process involving fluctuating electric fields. The loss of trapped low altitude protons, alpha particles and ions (Z 2) is controlled by coulombic energy loss in the atmosphere.

Randall, B. A.↗
NASA NTRSDate not supplied

Characterization of Naturally-Occurring Particles in the Nasa Langley 0.3-m Transonic Cryogenic Tunnel Using PTV

Naturally-occurring particles within the NASA Langley 0.3-m Transonic Cryogenic Tunnel are characterized for their aerodynamic performance using particle tracking velocimetry. Two sets of experiments were conducted to observe different behaviors of the particles. The normal shockwave emanating from the top surface of a supercritical airfoil was used to induce velocity lag in the particles, and the subsequent spatial decay of the velocity was used to estimate the effective diameter of the particles. Mean particle diameters between 1.6 and 1.9 𝝁m were measured, with sizes ranging from 0.2 to 3.5 𝝁m over the entire ensemble. The response of particles to separated flow was investigated. By operating in “high-lift” (low Mach number, high angle of attack) conditions with a semi-span airfoil, the ability of particles to detect separated flow on the upper surface of the airfoil was assessed. Transition from fully attached flow to fully separated flow was observed on the top surface of the airfoil accompanying a variation of angle of attack from 8° to 12°. Examination of velocity distributions indicates less than 10 percent of particle trajectories did not respond to the regions of separated flow. These results are promising, but further facility-specific work is needed to answer the broader question of particle tracking reliability.

Transonic↗
NASA NTRSDate not supplied

Characterization of Naturally-Occurring Particles in the NASA Langley 0.3-m Transonic Cryogenic Tunnel Using PTV

Naturally-occurring particles within the NASA Langley 0.3-m Transonic Cryogenic Tunnel are characterized for their aerodynamic performance using particle tracking velocimetry. Two sets of experiments were conducted to observe different behaviors of the particles. The normal shockwave emanating from the top surface of a supercritical airfoil was used to induce velocity lag in the particles, and the subsequent spatial decay of the velocity was used to estimate the effective diameter of the particles. Mean particle diameters between 1.6 and 1.9 𝝁m were measured, with sizes ranging from 0.2 to 3.5 𝝁m over the entire ensemble. The response of particles to separated flow was investigated. By operating in “high-lift” (low Mach number, high angle of attack) conditions with a semi-span airfoil, the ability of particles to detect separated flow on the upper surface of the airfoil was assessed. Transition from fully attached flow to fully separated flow was observed on the top surface of the airfoil accompanying a variation of angle of attack from 8° to 12°. Examination of velocity distributions indicates less than 10 percent of particle trajectories did not respond to the regions of separated flow. These results are promising, but further facility-specific work is needed to answer the broader question of particle tracking reliability.

Transonic↗
DOE OSTI2025

Simulating Alpha Particles Incident on MKID Chips for Quantum Sensitivity Analysis

• Background noise from ionizing decay poses challenges for MKIDs due to their sensitivity to small energy depositions. • Our group bakes the MKID housing lid in radon to study effects of alphas from daughter isotopes in the decay chain. • The impact of alpha particles on the chip depends on their energy, making their distribution key to characterizing and reducing noise in superconducting quantum devices.

Hall, Matthew [Southern California U.]↗
DOE OSTI2024

New graph-neural-network flavor tagger for Belle II and measurement of sin 2⁢𝜙 1 in 𝐵 0 → 𝐽/𝜓⁢𝐾$^0_ S$ decays

We present GFlaT, a new algorithm that uses a graph-neural-network to determine the flavor of neutral 𝐵 mesons produced in ϒ⁡(4⁢𝑆) decays. It improves previous algorithms by using the information from all charged final-state particles and the relations between them. We evaluate its performance using 𝐵 decays to flavor-specific hadronic final states reconstructed in a 362 fb −1 sample of electron-positron collisions collected at the ϒ⁡(4⁢𝑆) resonance with the Belle II detector at the SuperKEKB collider. We achieve an effective tagging efficiency of (37.40 ± 0.43 ± 0.36%), where the first uncertainty is statistical and the second systematic, which is 18% better than the previous Belle II algorithm. Demonstrating the algorithm, we use 𝐵 0 →𝐽/𝜓⁢𝐾$^0_ S$ decays to measure the mixing-induced and direct 𝐶⁢𝑃 violation parameters, 𝑆 = (0.724 ± 0.035 ± 0.009) and 𝐶 = (−0.035 ± 0.026 ± 0.029).

CP violation↗
DOE OSTI2024

Search for W′ bosons decaying to a top and a bottom quark in leptonic final states in proton-proton collisions at $ \sqrt{s} $ = 13 TeV

A search for W′ bosons decaying to a top and a bottom quark in final states including an electron or a muon is performed with the CMS detector at the LHC. The analyzed data correspond to an integrated luminosity of 138 fb$^{−1}$ of proton-proton collisions at a center-of-mass energy of 13 TeV. Good agreement with the standard model expectation is observed and no evidence for the existence of the W′ boson is found over the mass range examined. The largest observed deviation from the standard model expectation is found for a W′ boson mass ($ {m}_{{\textrm{W}}^{\prime }} $) hypothesis of 3.8 TeV with a relative decay width of 1%, with a local (global) significance of 2.6 (2.0) standard deviations. Upper limits on the production cross sections of W′ bosons decaying to a top and a bottom quark are set. Left- and right-handed W′ bosons with $ {m}_{{\textrm{W}}^{\prime }} $ below 3.9 and 4.3 TeV, respectively, are excluded at the 95% confidence level, under the assumption that the new particle has a narrow decay width. Limits are also set for relative decay widths up to 30%.[graphic not available: see fulltext]

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1982

Solar flare shocks in interplanetary space and solar flare particle events

Data on particle events resulting from three solar flares are examined to determine the effect of shocks on the population of protons at energies not less than 30 MeV. The arrival of the shock is found to mark the start of the decay phase of the particle event, and changes in particle anisotropy are found to be related to features in the shock structure. Two distinct modes of particle propagation are found to exist: a direct component, and a second component which has a time scale of days and is seen in two of the flares which also produced interplanetary shock. In addition, a model is described in which the protons are accelerated by the shocks, and it is shown to be in agreement with observations.

Evenson, P.↗
DOE OSTI2025

Study of η → π + π − l + l −

Using a sample of ( 10087 ± 44 ) × 10 6 J / ψ events accumulated with the BESIII detector, we analyze the decays η → π + π − l + l − ( l = e or μ ) via the process J / ψ → γ η . The branching fraction of η → π + π − e + e − is measured to be B ( η → π + π − e + e − ) = ( 3.07 ± 0.1 2 stat ± 0.1 9 syst ) × 10 − 4 . No signal events are observed for the η → π + π − μ + μ − decay, leading to an upper limit on the branching fraction of B ( η → π + π − μ + μ − ) < 4.0 × 10 − 7 at the 90% confidence level. Furthermore, the C P -violation asymmetry parameter is found to be A C P ( η → π + π − e + e − ) = ( − 4.04 ± 4.6 9 stat ± 0.1 4 syst ) % , showing no evidence of C P -violation with current statistics. Additionally, we extract the transition form factor from the decay amplitude of η → π + π − e + e − . Finally, axionlike particles are searched for via the decay η → π + π − a , a → e + e − , and upper limits on this branching fraction relative to that of η → π + π − e + e − are presented as a function of the axionlike particle mass in the range 5 – 200 MeV / c 2 . Published by the American Physical Society 2025

Ablikim, M.↗