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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Electromagnetic production of hyperon resonances

The study of hyperon resonances has entered a new era of precision with advent of high-statistics photoproduction data from the CLAS detector at Jefferson Lab. These data have multi-particle final states, allowing clean identification of exclusive reactions associated with strange mesons and baryons. Examples of physics results are: evidence for isospin interference in the decay of the {Lambda}(1405) resonance; a strong suggestion of meson cloud effects in the structure of the {Sigma}(1385) resonance; data from K* photoproduction that will test the existence of the purported K{sub 0}(800) meson. Properties of other hyperon resonances will also be studied in the near future.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Note: Experiments in hard x-ray chemistry: In situ production of molecular hydrogen and x-ray induced combustion

We have successfully loaded H{sub 2} into a diamond anvil cell at high pressure using the synchrotron x-ray induced decomposition of NH{sub 3}BH{sub 3}. In a second set of studies, radiation-assisted release of O{sub 2} from KCLO{sub 3}, H{sub 2} release from NH{sub 3}BH{sub 3}, and reaction of these gases in a mixture of the reactants to form liquid water using x-rays at ambient conditions was observed. Similar observations were made using a KCLO{sub 3} and NaBH{sub 4} mixture. Depending on reaction conditions, an explosive or far slower reaction producing water was observed.

08 HYDROGEN↗
DOE OSTI2011

Heavy-quark production in p + p and energy loss and flow of heavy quarks in Au + Au collisions at sqrt(s_NN)=200 GeV.

Transverse momentum spectra of electrons (p{sub T}{sup e}) from semileptonic weak decays of heavy-flavor mesons in the range of 0.3 < p{sub T}{sup e} < 9.0 GeV/c have been measured at midrapidity (|y| < 0.35) by the PHENIX experiment at the Relativistic Heavy Ion Collider in p+p and Au+Au collisions at {radical}s{sub NN} = 200 GeV. In addition, the azimuthal anisotropy parameter v{sub 2} has been measured for 0.3 < p{sub T}{sup e} < 5.0 GeV/c in Au+Au collisions. The substantial modification in the p{sub T}{sup e} spectra in Au+Au compared with p+p collisions as well as the nonzero v{sub 2} indicate substantial interactions and flow of heavy quarks in traversing the produced medium. Comparisons of these observables with detailed theoretical calculations can be used to identify the nature of these interactions and to quantify their extent.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Global parameterization and validation of a two-leaf light use efficiency model for predicting gross primary production across FLUXNET sites: TL-LUE Parameterization and Validation

We present the first extended validation of satellitemicrowave (MW) liquidwater path (LWP) for low nonprecipitating clouds, from four operational sensors, against ship-borne observations from a three-channel MW radiometer collected along ship transects over the northeast Pacific during May–August 2013. Satellite MW retrievals have an overall correlation of 0.84 with ship observations and a bias of 9.3 g/m2. The bias for broken cloud scenes increases linearly with water vapor path and remains below 17.7 g/m2. In contrast, satelliteMWLWP is unbiased in overcast scenes with correlations up to 0.91, demonstrating that the retrievals are accurate and reliable under these conditions. Satellite MW retrievals produce a diurnal cycle amplitude consistent with ship-based observations (33 g/m2). Observations taken aboard extended ship cruises to evaluate not only satellite MW LWP but also LWP derived from visible/infrared sensors offer a new way to validate this important property over vast oceanic regions.

Zhou, Yanlian↗
DOE OSTI2012

Search for anomalous Wtb couplings in single top quark production in p(p)over-bar collisions at root s=1.96 TeV

We present new direct constraints on a general Wtb interaction using data corresponding to an integrated luminosity of 5.4 fb{sup -1} collected by the D0 detector at the Tevatron p{bar p} collider. The standard model provides a purely left-handed vector coupling at the Wtb vertex, while the most general, lowest dimension Lagrangian allows right-handed vector and left- or right-handed tensor couplings as well. We obtain precise limits on these anomalous couplings by comparing the data to the expectations from different assumptions on the Wtb coupling.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Target and double spin asymmetries of deeply virtual π 0 production with a longitudinally polarized proton target and CLAS

The target and double spin asymmetries of the exclusive pseudoscalar channel e→p→→epπ0 were measured for the first time in the deep-inelastic regime using a longitudinally polarized 5.9 GeV electron beam and a longitudinally polarized proton target at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS). The data were collected over a large kinematic phase space and divided into 110 four-dimensional bins of Q2, xB, -t and Φ. Large values of asymmetry moments clearly indicate a substantial contribution to the polarized structure functions from transverse virtual photon amplitudes. The interpretation of experimental data in terms of generalized parton distributions (GPDs) provides the first insight on the chiral-odd GPDs H˜T and ET, and complement previous measurements of unpolarized structure functions sensitive to the GPDs HT and E¯T. These data provide a crucial input for parametrizations of essentially unknown chiral-odd GPDs and will strongly influence existing theoretical calculations based on the handbag formalism.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Mitigation of nonthermal plasma production to measure the pulsed magnetic field threshold for the thermal formation of plasma from thick aluminum surfaces

Untangling the roles of different plasma formation mechanisms in high-current electrical discharges requires controlling each mechanism and isolating its effects. Recent experiments use this method to find that thermal formation of plasma occurs from 6061-alloy Al conductors by ohmic heating when the surface field reaches a magnetic field threshold of 2.2 MG (independently of {partial_derivative}B/{partial_derivative}t ranging from 30 to 80 MG/{mu}s) [T. J. Awe et al., Phys. Rev. Lett. 104, 035001 (2010)]. The experiments pulse 1.0 MA peak current on the surface of thick ({approx}1.0 mm diameter) aluminum rods in 100 ns. Strong electric fields are necessarily introduced, and precursor plasma may form (e.g., from arcing electrical contacts). To ensure plasma formation is predominantly thermal, a systematic study of multiple combinations of high-current electrodes and central-rod profiles was completed. Data from multiple diagnostics show that the time and location of plasma formation strongly correlate with the hardware combination used. An extensive dataset (greater than 100 shots) enabled numerous hypotheses to be tested regarding plasma formation mechanisms. For hardware with compressed, large-diameter current joints, plasma formation is a predominantly thermal process driven by ohmic heating.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Hard exclusive neutral pion production at Jefferson Lab Hall A

We present measurements of the ep{yields}ep{pi}{sup 0} cross section extracted at two values of four-momentum transfer Q{sup 2} = 1.9 GeV{sup 2} and Q{sup 2} = 2.3 GeV{sup 2} at Jefferson Lab Hall A. The kinematic range allows to study the evolution of the cross section as a function of Q{sup 2} and W. Results will be confronted with Regge inspired calculations and GPD predictions. An intepretation of our data within the framework of semi-inclusive deep inelastic scattering has also been attempted.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗