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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Searches for direct slepton production in the compressed-mass corridor in $\sqrt{\textrm{s}}$ = 13 TeV pp collisions with the ATLAS detector

This paper presents searches for the direct pair production of charged light-flavour sleptons, each decaying into a stable neutralino and an associated Standard Model lepton. The analyses focus on the challenging ``corridor'' region, where the mass difference, $Δm$, between the slepton ($\tilde{e}$ or $\tildeμ$) and the lightest neutralino ($\tildeχ^{0}_{1}$) is less or similar to the mass of the $W$ boson, $m(W)$, with the aim to close a persistent gap in sensitivity to models with $Δm \lesssim m(W)$. Events are required to contain a high-energy jet, significant missing transverse momentum, and two same-flavour opposite-sign leptons ($e$ or $μ$). The analysis uses $pp$ collision data at $\sqrt{s} = 13$ TeV recorded by the ATLAS detector, corresponding to an integrated luminosity of 140 fb$^{-1}$. Several kinematic selections are applied, including a set of boosted decision trees. These are each optimised for different $Δm$ to provide expected sensitivity for the first time across the full $Δm$ corridor. The results are generally consistent with the Standard Model, with the most significant deviations observed with a local significance of 2.0 $σ$ in the selectron search, and 2.4 $σ$ in the smuon search. While these deviations weaken the observed exclusion reach in some parts of the signal parameter space, the previously present sensitivity gap to this corridor is largely reduced. Constraints at the 95% confidence level are set on simplified models of selectron and smuon pair production, where selectrons (smuons) with masses up to 300 (350) GeV can be excluded for $Δm$ between 2 GeV and 100 GeV.

hadron-hadron scattering↗
DOE OSTI2023

Spin density matrix elements in exclusive $\rho ^0$ meson muoproduction

We report on a measurement of Spin Density Matrix Elements (SDMEs) in hard exclusive $\rho ^0$ meson muoproduction at COMPASS using 160 GeV/c polarised μ + and μ – beams impinging on a liquid hydrogen target. The measurement covers the kinematic range 5.0 GeV/c 2 < W < 17.0 GeV/c 2 , 1.0 (GeV/c) 2 < $\mathrm{Q}$ 2 < 10.0 (GeV/c) 2 and 0.01 (GeV/c) 2 < $p_{\textrm{T}}^2$ < 0.5 (GeV/c) 2 . Here, W denotes the mass of the final hadronic system, $\mathrm{Q}$ 2 the virtuality of the exchanged photon, and $p_{\textrm{T}}$ the transverse momentum of the $\rho ^0$ meson with respect to the virtual-photon direction. The measured non-zero SDMEs for the transitions of transversely polarised virtual photons to longitudinally polarised vector mesons ($\gamma ^*_T \rightarrow V^{ }_L$) indicate a violation of s-channel helicity conservation. Additionally, we observe a dominant contribution of natural-parity-exchange transitions and a very small contribution of unnatural-parity-exchange transitions, which is compatible with zero within experimental uncertainties. The results provide important input for modelling Generalised Parton Distributions (GPDs). In particular, they may allow one to evaluate in a model-dependent way the role of parton helicity-flip GPDs in exclusive $\rho ^0$ production.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Search for a heavy Higgs boson decaying into a Z boson and another heavy Higgs boson in the $\ell \ell bb$ and $\ell \ell WW$ final states in pp collisions at $\sqrt{s}=13$ $\text {TeV}$ with the ATLAS detector

A search for a heavy neutral Higgs boson, A decaying into a Z boson and another heavy Higgs boson, H, is performed using a data sample corresponding to an integrated luminosity of 139 fb-1 from proton–proton collisions at $\sqrt{s} = 13$ TeV recorded by the ATLAS detector at the LHC. The search considers the Z boson decaying into electrons or muons and the H boson into a pair of b-quarks or W bosons. The mass range considered is 230–800 $\text {GeV}$ for the A boson and 130–700 $\text {GeV}$ for the H boson. The data are in good agreement with the background predicted by the Standard Model, and therefore 95% confidence-level upper limits for $\sigma \times B(A\rightarrow ZH)\times B(H\rightarrow bb \; \text {or} \; H \rightarrow WW)$ are set. The upper limits are in the range 0.0062–0.380 pb for the $H\rightarrow bb$ channel and in the range 0.023–8.9 pb for the $H\rightarrow WW$ channel. An interpretation of the results in the context of two-Higgs-doublet models is also given.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Nuclear Data Sheets for A=194

Experimental nuclear structure and decay data are evaluated for all of 14 known nuclides of mass 194 (Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po, At, Rn). Detailed evaluated spectroscopic information is presented for each reaction and decay experiment, and by combining all the available data, recommended values are provided for energies, spins and parities and half-lives of levels, together with energies, branching ratios and multipolarities of gamma radiations from the levels, and characteristics of beta and alpha radiations in radioactive decays. No excited states have yet been identified in 194 Ta, 194 W, and 194 Rn. Only limited spectroscopic data are available for 194 Re, with a 45–μs isomer identified, but its absolute energy yet to be determined. Only two levels at unknown absolute energies are reported for 194 At, both of which are isomeric but neither can be unambiguously identified as the ground state. Data are scarce for 194 Os, 194 Bi and 194 Po, while 194 Pt, 194 Au, 194 Hg, 194 Tl and 194 Pb are well studied through decays and reactions. For 194 Ir, although a major (n, γ), E=thermal study and two particle-transfer studies provide large amounts of spectral data, still several problematic issues are found in the assignment of multipolarities for the secondary gamma transitions in the (n, γ) study by 2008Ba25, 1998Ba85 and 1998Ba42, all from the same group. Some issues have been resolved by the evaluators, but we suggest that further experimental work is needed on 194 Ir structure to resolve standing issues, and verify the conclusions made by 2008Ba25. Furthermore, our attempt to contact the prime authors of the 2008Ba25 paper was not successful. The present work supersedes all the earlier evaluations of A=194 nuclides by 2006Si17, 1996Br26, 1989Si01 and 1972Au11.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

First measurement of polarized spin-density matrix elements and differential cross sections dσ/dt in ω photoproduction off the proton for 2.7 < Eγ < 5.2 GeV using CLAS at Jefferson Lab

We report on the differential cross sections dσ/dt, the unpolarized spin-density matrix elements ρ 00 0 , ρ 1 − 1 0 , Re ρ 10 0 , and the first extraction of the polarized elements Im ρ 10 3 , Im ρ 1 − 1 3 for the reaction γp → pω using the CLAS spectrometer at Jefferson Laboratory. The ω mesons were detected in their dominant charged decay mode, ω → π + π − π 0 , and all t-dependent results are presented in a fine binning for incident photon energies between 2.73 and 5.16 GeV (corresponding to the center-of-mass energy range W ∈ [ 2.45, 3.25 ] GeV). All matrix elements are first measurements for − t > 0.6 GeV2. Moreover, differential cross sections dσ/d(cos Θ c . m . ω ) and the corresponding angle-dependent unpolarized spin-density matrix elements in the Adair frame are presented for the incident photon energy range 1.56–3.80 GeV (corresponding to W ∈ [ 1.95, 2.83 ] GeV). These new ω photoproduction data are consistent with earlier CLAS results but extend the energy range well beyond the nucleon resonance region into the Regge regime. The comparison with Regge-theory-based model predictions shows that the new data impose more stringent constraints on our understanding of ω photoproduction.

Hu, T.↗
DOE OSTI2022

Sub-percentage measure of distances to redshift of 0.1 by a new cosmic ruler

ABSTRACT Distance-redshift diagrams probe expansion history of the Universe. We show that the stellar mass-binding energy (massE) relation of galaxies proposed in our previous study offers a new distance ruler at cosmic scales. By using elliptical galaxies in the main galaxy sample of the Sloan Digital Sky Survey Data Release 7, we construct a distance-redshift diagram over the redshift range from 0.05 to 0.2 with the massE ruler. The best-fit dark energy density is 0.675 ± 0.079 for flat Λ-cold dark matter (ΛCDM) model, consistent with those by other probes. At the median redshift of 0.11, the median distance is estimated to have a fractional error of 0.34 per cent, much lower than those by supernova (SN) Ia and baryonic acoustic oscillation (BAO) and even exceeding their future capability at this redshift. The above low-$\mathit{ z}$ measurement is useful for probing dark energy that dominates at the late Universe. For a flat dark energy equation of state model (flat wCDM), the massE alone constrains w to an error that is only a factor of 2.2, 1.7, and 1.3 times larger than those by BAO, SN Ia, and cosmic microwave background (CMB), respectively.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Observation of the p η ' Cusp in the New Precise Beam Asymmetry Σ Data for γ p → p η

Data on the beam asymmetry Σ in the photoproduction of η mesons off protons are reported for tagged photon energies from 1130 to 1790 MeV (mass range from W = 1748 MeV to W = 2045 MeV). The data cover the full solid angle that allows for a precise moment analysis. For the first time, a strong cusp effect in a polarization observable has been observed that is an effect of a branch-point singularity at the pη' threshold [E γ = 1447 MeV (W = 1896 MeV)]. Here, the latest BnGa partial wave analysis includes the new beam asymmetry data and yields a strong indication for the N(1895)1/2 – nucleon resonance, demonstrating the importance of including all singularities for a correct determination of partial waves and resonance parameters.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1971

Comments on an association in Vela

Evidence for an association near the Vela pulsar rests on the H-R diagram. Definite bunching occurs around the mean line. However this evidence is not supported by correlation of proper motions in the region. If the Vela pulsar is a member of this association, a rather large mass is implied, about 10 solar masses.

Straka, W. C.↗
NASA NTRS1972

Binary nature of the B supergiant in the error box of the Vela X-ray source.

Spectroscopic and photometric observations were carried out for HD 77581, a B0.5 Ib star located in the error box of the X-ray source 2U 0900-40. HD 77581 is identified as spectroscopic binary with a provisional period of 7.0 days and a semiamplitude of 26 km/sec. The minimum mass of the secondary star is near 1.4 solar mass.

Hiltner, W. A.↗
NASA NTRS1975

Effects of darkening processes on surfaces of airless bodies

We find the lunar darkening process could be due neither to simple addition of impact-melted glass nor to addition of devitrified glass to crushed lunar rock. There is evidence that lunar soil grains have thin, very light-absorbing coatings that mask absorption bands, seen in the reflection spectra of freshly crushed lunar rock, in the same manner as they are masked in the spectra of lunar soils. We believe the processes that produce these coatings are (1) deposition of atoms sputtered from lunar soil grains by solar wind particles and (2) deposition of vapor species vaporized from lunar soil grains by micrometeoritic impacts. We describe an apparent new type of fractionation that occurs during deposition of sputtered atoms. This fractionation favors retention of higher mass atoms over lower mass atoms, and appears to be a linear function of mass.

Cassidy, W.↗
NASA NTRS1977

Determination of the critical loads of shells by nondestructive methods

Two methods for determining the location of and load level to produce instability of compressed cylindrical shells are presented. The first relates the variation in the wall normal stiffness as a function of applied compressive force to the critical load. It uses the distribution of stiffness over the surface of the shell as a guide to buckle location. The second method associates the local dynamic mass with instability behavior. The test data presented show that either method will give excellent prediction capability from low-load-level data for shells of orthodox form. Neither method appears to apply to spirally stiffened shells. This is thought to be due to the fact that there is a substantial difference between the buckle pattern under axial compression and the imperfection shape induced by the normal displacement which is used to ascertain the wall stiffness and the dynamic mass.

Horton, W. H.↗
NASA NTRS1983

The extraordinary extragalactic supernova remnant in NGC 4449. II - X-ray and optical investigations

Einstein Observatory X-ray observations indicate that the SNR in NGC 4449 is the most luminous X-ray, as well as optical and radio, SNR known. New optical spectroscopy, together with the X-ray data, suggest this exceptional luminosity to be due to chemically enriched material at unusually high densities. A model is proposed in which this SNR resulted from the explosion of a massive star in a medium of nearly 25/cu cm density about 100 years ago. The chemistry in question further suggests that the SNR in NGC 4449 resulted from the explosion of a star whose mass was greater than 25 solar masses.

Blair, W. P.↗
NASA NTRS1982

Diffusion instability in a bimodal disc

A simplified model of radial diffusion in a planetary disk with a bimodal size distribution is presented. The large particle component excites the small particles' dispersion velocity via gravitational scattering. The resulting small particle viscous stress goes through a maximum near optical depth = sq root 3. Such a stress profile promotes the development of high and low optical depth zones. The resulting ringlet appearance is due primarily to the distribution of small particles, which produce most of the optical depth but may constitute only a minor portion of system mass.

Ward, W. R.↗
NASA NTRS1985

Impact experiments. I - Ejecta velocity distributions and related results from regolith targets

Results are reported of laboratory measurements of the velocity distributions of powdery ejecta of 14 impacts into powders simulating regolith in near vacuum. The impact velocities ranged from 5-2321 m/sec, a velocity range believed prevalent in the early solar system. The powder was mechanically similar to lunar regolith. The projectiles comprised harder materials than the regolith, i.e., pyrex spheres, basalt spheres and cylinders, and igneous rocks. High-speed photography was employed to record the events. The differences between the present results and those from hypervelocity impacts are discussed in detail. Notably, an impact velocity threshold was detected between 10-30 m/sec, below which the amount of ejecta is less than the projectile mass.

Hartmann, W. K.↗
NASA NTRS1986

Polar platform payload requirements in the 1990's

NASA's Earth Orbiting System (EOS) and NOAA's operational payloads represent two of the major users of the Space Station Polar Platform capabilities. The EOS program will be designed for Shuttle launch, servicing and on-orbit augmentation, while the NOAA's payload will be designed for the operational monitoring of the earth's atmosphere, oceans, and land masses. An overview is given of both the EOS and NOAA platform programs as well as the implied platform requirements. It is concluded that the generic platform design must be capable of operating at altitudes ranging from Shuttle altitudes to NOAA altitudes (approximately 850 km). In addition, it must be able to accommodate approximately 5000 kg of payload mass, provide 5000 W of continuous power and up to 13 kW of peak power for short durations, and store and transmit data at rates up to 300 Mbps.

Vane, D.↗
NASA NTRS1987

Star formation rates as a function of galaxy mass

Correlations were found between the colors and absolute magnitudes of spiral galaxies. Using optical and/or near IR (1.6 micron) colors, it was found that lower luminosity spirals are systematically bluer than higher luminosity spirals. Infrared Astronomy Satellite (IRAS) far IR luminosities were used to investigate the suggestion that one prime cause of these color-absolute magnitude correlations is a systematic variation with galaxy mass of the current star formation rate (SFR) per unit mass. To the extent that the IRAS fluxes actually measure disk SFR, no correlation of SFR/unit mass and galaxy mass was found. Other possible explanations of the color-absolute magnitude correlations are discussed, as well as caveats on the use of IRAS fluxes as a means of comparing SFRs in galaxies of differing mass.

Romanishin, W.↗
NASA NTRS1986

Evolution of super-Jupiters

The physics of the interiors of Jovian-class objects is reviewed, and its extension to substellar objects is discussed. Some results are presented for objects cooling from effective temperatures starting at 2500 K. The interior calculations are coupled to model atmosphere surface conditions computed by Lunine; the latter are continued to higher temperatures and pressures in the ideal gas region and are then matched by entropy to the strongly-coupled interior region. Except in the planetary-mass models, this transition region occupies a negligible fraction of the total mass. For the observed parameters of VB8B, only models with masses in excess of 0.05 solar mass have cooling ages above a billion years. Thus, for plausible VB8B lifetimes, this object is likely to be close to the critical hydrogen-ignition mass.

Hubbard, W. B.↗