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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 OSTI2026

Tau-Jet Matching and Tag-and-Probe Tau Tagging Efficiencies for HH→bbτ+τ− Searches Using Run 3 CMS Scouting Data

We are studying tau-jet matching efficiency and tau tagging efficiency for the search for Higgs boson pair production in the HH→bbτ+τ− decay channel using Run 3 CMS scouting data. Collision events in the CMS detector produce many particle candidates, so jets are clustered using the anti-kT algorithm to identify possible tau signatures. In Monte Carlo simulation, tau-jet matching efficiency can be measured by comparing generated taus to reconstructed jets. In actual collision data, however, generated taus are not available, so we use a tag-and-probe method with Z→τ+τ− candidate events. In this method, one tau candidate is used as the tag and the other as the probe. The invariant mass of the tau-pair candidates is plotted and fitted with signal and background functions to estimate the number of real tau events and determine the tagging efficiency. By comparing efficiencies in data and Monte Carlo simulation, this work helps evaluate the performance of scouting-based tau reconstruction and tau tagging for future HH→bbτ+τ− searches.

Bellot, Annella [North Central Coll.; Fermilab]↗
DOE OSTI2026

Tau-Jet Matching and Tag-and-Probe Tau Tagging Efficiencies for HH→bbτ+τ− Searches Using Run 3 CMS Scouting Data

We are studying tau-jet matching efficiency and tau tagging efficiency for the search for Higgs boson pair production in the HH→bbτ+τ− decay channel using Run 3 CMS scouting data. Collision events in the CMS detector produce many particle candidates, so jets are clustered using the anti-kT algorithm to identify possible tau signatures. In Monte Carlo simulation, tau-jet matching efficiency can be measured by comparing generated taus to reconstructed jets. In actual collision data, however, generated taus are not available, so we use a tag-and-probe method with Z→τ+τ− candidate events. In this method, one tau candidate is used as the tag and the other as the probe. The invariant mass of the tau-pair candidates is plotted and fitted with signal and background functions to estimate the number of real tau events and determine the tagging efficiency. By comparing efficiencies in data and Monte Carlo simulation, this work helps evaluate the performance of scouting-based tau reconstruction and tau tagging for future HH→bbτ+τ− searches.

Bellot, Annella [North Central Coll.; Fermilab]↗
NASA NTRS1972

An empirical model of energetic solar proton fluxes with applications to earth orbiting spacecraft

An empirical model for energetic solar proton fluxes is presented. With this model, the effects of such protons on geocentric space missions, to be flown during the next solar active period (1966-1983) and with orbits involving partial magnetospheric shielding, may be estimated. A synoptic background review is given, followed by a detailed discussion of the model's analytic development. Also given are comments on the model's use, errors, uncertainties, and limitations, including sample calculations which demonstrate the application of specific or general project missions. Finally, for circular trajectories, percentage exposure maps are presented, depicting fractional mission times spent outside particular L-shells as functions of orbit altitude and inclination.

Stassinopoulos, E. G.↗
NASA NTRS1974

Empirical solar proton model for orbiting spacecraft applications

An empirical model for energetic solar proton fluxes is presented. With this model the effects of such protons on geocentric space missions, to be flown during the next solar active period (1977-1983), and with orbits involving partial magnetospheric shielding, may be estimated. A synoptic background review is given, followed by a detailed discussion of the model's use, errors, uncertainties, and limitations, including sample calculations which demonstrate the application of specific or general project missions. Finally, for circular trajectories, percentage exposure maps are presented, depicting fractional mission times spent outside particular L shells as functions of orbit altitude and inclination.

Stassinopoulos, E. G.↗
NASA NTRS1976

Surface chemistry of selected lunar regions

A completely new analysis has been carried out on the data from the Apollo 15 and 16 gamma ray spectrometer experiments. The components of the continuum background have been estimated. The elements Th, K, Fe and Mg give useful results; results for Ti are significant only for a few high Ti regions. Errors are given, and the results are checked by other methods. Concentrations are reported for about sixty lunar regions; the ground track has been subdivided in various ways. The borders of the maria seem well-defined chemically, while the distribution of KREEP is broad. This wide distribution requires emplacement of KREEP before the era of mare formation. Its high concentration in western mare soils seems to require major vertical mixing.

Bielefeld, M. J.↗
NASA NTRS1976

Noise propagation in urban and industrial areas

Noise propagation in streets and the discrepancies between theoretical analyses and field measurements are discussed. A cell-model is used to estimate the general background level of noise due to vehicular sources distributed over the urban area.

Davies, H. G.↗
NASA NTRS1976

Surface chemistry of selected lunar regions

A completely new analysis has been carried out on the data from the Apollo 15 and 16 gamma ray spectrometer experiments. The components of the continuum background have been estimated. The elements Th, K, Fe and Mg give useful results; results for Ti are significant only for a few high Ti regions. Errors are given, and the results are checked by other methods. Concentrations are reported for about sixty lunar regions; the ground track has been subdivided in various ways. The borders of the maria seem well-defined chemically, while the distribution of KREEP is broad. This wide distribution requires emplacement of KREEP before the era of mare formation. Its high concentration in western mare soils seems to require major vertical mixing.

Bielefeld, M. J.↗
NASA NTRS1976

Surface chemistry of selected lunar regions

A completely new analysis has been carried out on the data from the Apollo 15 and 16 gamma-ray spectrometer experiments. The components of the continuum background have been estimated. The elements Th, K, Fe, and Mg give useful results; for Ti are significant only for a few high-Ti regions. Errors are given, and the results are checked by other methods. Concentrations are reported for about 60 lunar regions; the ground track has been subdivided in various ways. The borders of the maria seem well-defined chemically, while the distribution of KREEP is broad. This wide distribution requires emplacement of KREEP before the era of mare formation. Its high concentration in western mare soils seems to require major vertical mixing.

Bielefeld, M. J.↗
NASA NTRS1979

Fluctuations in microwave background radiation due to secondary ionization of the intergalactic gas in the universe

Secondary heating and ionization of the intergalactic gas at redshifts z approximately 10-30 could lead to the large optical depth of the Universe for Thomson scattering and could smooth the primordial fluctuations formed at z approximately 1500. It is shown that the gas motions connected with the large scale density perturbations at z approximately 10-15 must lead to the generation of secondary fluctuations of microwave background. The contribution of the rich clusters of galaxies and young galaxies to the fluctuations of microwave background is also estimated.

Sunyayev, R. A.↗
NASA NTRS1985

Cyg X-3: Not seen in high-energy gamma rays by COS-B

COS-B had Cyg X-3 within its field of view during 7 observation periods between 1975 and 1982 for in total approximately 300 days. In the skymaps (70 meV E 5000 meV) of the Cyg-X region produced for each of these observations and in the summed map, a broad complex structure is visible in the region 72 deg approximately less than 1 approximately less than 85 deg, approximately less than 5 deg. No resolved source structure is visible at the position of Cyg X-3, but a weak signal from Cyg X-3 could be hidden in the structured gamma-ray background. Therefore, the data has been searched for a 4.8 h timing signature, as well as for a source signal in the sky map in addition to the diffuse background structure as estimated from tracers of atomic and molecular gas.

Hermsen, W.↗
NASA NTRS1987

Generation of plasma waves by thick-target electron beams, and the expected radiation signature

The production of plasma waves by a nonthermal beam of high-energy electrons injected into a background thermal plasma was investigated. The coupled kinetic equations for nonthermal electrons were solved, and the level of the plasma waves produced by the bump-on-tail instability arising as a result of the Coulomb collisions of nonthermal electrons with background plasma was estimated. In addition, the radiation signatures of these waves were examined. It is shown that the wave-particle interactions have a significant effect on the overall distribution of the electrons and that it is unlikely that such effects can be discerned in the observed bremsstrahlung or synchrotron radiation of the nonthermal electrons. However, a significant fraction of the energy lost by the beam is transferred to plasma waves and is then dissipated by the thermal plasma.

Hamilton, Russell J.↗
NASA NTRS1989

X-ray morphologies of Abell clusters

Results are presented for X-ray measurements made with the Einstein Observatory's IPC for a sample of 49 Abell clusters, which were used to determine quantitative measures of two morphological parameters of these clusters, the orientation and ellipticity. Consideration is given to the techniques used for estimating and removing background noise in the images and for determining the variation of these parameters with the flux level of a cluster. It was found that most clusters are clearly flattened; for 20 of these clusters, the orientation was unambiguously determined. A catalog of cluster properties is presented.

Mcmillan, S. L. W.↗
NASA NTRS1991

A hydrodynamic approach to cosmology - Texture-seeded cold dark matter and hot dark matter cosmogonies

Hydrodynamical simulations of galaxy formation in a texture-seeded cosmology are presented, with attention given to Omega = 1 galaxies dominated by both hot dark matter (HDM) and cold dark matter (CDM). The simulations include both gravitational and hydrodynamical physics with a detailed treatment of collisional and radiative thermal processes, and use a cooling criterion to estimate galaxy formation. Background radiation fields and Zel'dovich-Sunyaev fluctuations are explicitly computed. The derived galaxy mass function is well fitted by the observed Schechter luminosity function for a baryonic M/L of 3 and total M/L of 60 in galaxies. In both HDM and CDM texture scenarios, the 'galaxies' and 'clusters' are significantly more strongly correlated than the dark matter due to physical bias processes. The slope of the correlation function in both cases is consistent with observations. In contrast to Gaussian models, peaks in the dark matter density distributrion are less correlated than average.

Cen, R. Y.↗
NASA NTRS1992

QSO's to B less than 22 and the cosmic x ray background radiation: A fluctuations correlation approach

The contribution of faint Quasi Stellar Objects (QSO's) and other discrete sources to the cosmic X-Ray Background (XRB) is estimated using an optically selected QSO sample in SA 68.2 in conjunction with archived x-ray images from the Einstein Image Proportional Counter (IPC). A new generalization of the 'x-ray image stacking' technique is employed; this new approach tests for a positional 'correlation' between positive x-ray fluctuations in the IPC images, and the locations of the optically selected QSO's. Correlation with thirty SA 68.2 QSO's permits a highly sensitive measurement of the ensemble mean x-ray flux for QSO's with 19 less than B(sub J) less than 22. Although the IPC images are of modest depth, a limiting sensitivity 1.2 times 10 to the minus 14th power erg/sec/sq cm (0.3 to 3.5 keV) is effectively archieved comparable to that of the Rosat medium deep surveys.

Anderson, S. F.↗
NASA NTRS1984

Pioneer 10 and Voyager Observations of the Interstellar Medium in Scattered Emission of the H 584 A and H Lya 1216 A Lines

The combination of Pioneer photometric and Voyager spectrometric observations of EUV interstellar-interplanetary emissions in the region beyond 5 AU have been applied to a determination of atomic hydrogen and helium densities. These density estimates obtained from direct measurement of scattered radiation depend on absolute calibration of the instruments, in the same way as other earlier determinations based on the same method. However. we have combined the spacecraft data with daily full sun averages of the H Lya 1216 A line obtained by the Solar Mesospheric Explorer (SME) satellite, to obtain a measure of atomic hydrogen density independent of instrument absolute calibration. The method depends on observations of long and short term temporal variability of the solar line over a 1 year period, and the fact that the ISM is optically thick. The density estimates from preliminary work on these observations are (H) = 0.12 cm(sup 2) and (He) = .016 cm(sup 2), giving a density ratio close to the cosmic abundance value, in contrast to some earlier results indicating a depletion of atomic hydrogen. We have obtained estimates of galactic background emissions in the signals of both spacecraft.

Shemansky, D. E.↗
NASA NTRS1997

Performance of an INTEGRAL spectrometer model

Model calculations for the INTEGRAL spectrometer (SPI) onboard the future INTErnational Gamma Ray Astrophysics Laboratory (INTEGAL) are presented, where the sensitivity for narrow lines is based on estimates of the background level and the detection efficiency. The instrumental background rates are explained as the sum of various components that depend on the cosmic ray intensity and the spectrometer characteristics, such as the mass distribution around the Ge detectors, the passive material, the characteristics of the detector system and the background reduction techniques. Extended background calculations were performed with Monte Carlo simulations and using semi-empirical and calculated neutron and proton cross sections. In order to improve the INTEGRAL spectrometer sensitivity, several designs and background reduction techniques were compared for an instrument with a fixed detector volume.

Jean, P.↗
NASA NTRS2005

Atmospheric Hydroperoxides in West Antarctica: Links to Stratospheric Ozone and Atmospheric Oxidation Capacity

The troposphere above the West Antarctic Ice Sheet (WAIS) was sampled for hydroperoxides at 21 locations during 2-month-long summer traverses from 2000 to 2002, as part of US ITASE (International Transantarctic Scientific Expedition). First time quantitative measurements using an HPLC method showed that methylhydroperoxide (MHP) is the only important organic hydroperoxide occurring in the Antarctic troposphere, and that it is found at levels ten times those previously predicted by photochemical models. During three field seasons, means and standard deviations for hydrogen peroxide (H2O2) were 321+/-158 pptv, 650+/-176 pptv and 330+/-147 pptv. While MHP was detected, but not quantified in December 2000, levels in summer 2001 and 2002 were 317+128 pptv and 304+/-172.2 pptv. Results from firn air experiments and diurnal variability of the two species showed that atmospheric H2O2 is significantly impacted by a physical snow pack source between 76 and 90degS, whereas MHP is not. We show strong evidence of a positive feedback between stratospheric ozone and H2O2 at the surface. Between November-27 and December-12 in 2001, when ozone column densities dropped below 220 DU (means in 2000 and 2001 were 318 DU and 334 DU, respectively), H2O2 was 1.7 times that observed in the same period in 2000 and 2002, while MHP was only 80% of the levels encountered in 2002. Photochemical box model runs suggest that NO and OH levels on WAIS are closer to coastal values, while Antarctic Plateau levels are higher, confirming that region to be a highly oxidizing environment. The modeled sensitivity of H2O2 and particularly MHP to NO offers the potential to use atmospheric hydroperoxides to constrain the NO background and thus estimate the past oxidation capacity of the remote atmosphere. Index Terms: 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry; 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 1610 Global Change: Atmosphere (03 15,0325); 0736 Cryosphere: Snow (1827, 1863); 0724 Cryosphere: Ice Cores (4932) Keywords: hydrogen peroxide, methylhydroperoxide, Antarctica, air-snow exchange, stratospheric ozone, atmospheric oxidation capacity

Frey, Markus M.↗