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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Transverse spin physics at CLAS and CLAS12

We present ongoing and future measurement of spin-azimuthal asymmetries in semi-inclusive production of pions in deep inelastic scattering using the CLAS detector at the Thomas Jefferson National Accelerator Facility (JLab). The azimuthal modulations of the double and single spin asymmetries have been measured in a wide kinematic range, providing access to transverse momentum distributions of partons. An extensive experimental program has been proposed for the upgraded JLab, which will allow precision studies of the transverse structure of the nucleon.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Studies of Partonic Transverse Momentum and Spin Structure of the Nucleon at HERMES

The investigation of the partonic degrees of freedom beyond collinear approximation (3D description) has been gained increasing interest in the last decade. At the HERMES experiment, azimuthal single-spin asymmetries of pions and charged kaons produced in semi-inclusive deep-inelastic scattering of electrons and positrons off a transversely (polarized) hydrogen and deuterium target have been measured. Such asymmetries provide new insights on crucial aspects of the parton dynamics. By measuring various hadron types in the initial and final states, flavor sensitivity is achieved. Evidence is reported of the poorly known transversity function and of naive-T-odd transverse-momentum-dependent parton distribution functions related to spin-orbit effects. Evidence of spin-orbit effects in quark fragmentation is also observed, which are opposite in sign for favored and disfavored processes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

NJL-jet model calculation of quark fragmentation to hadrons

A description of fragmentation processes of quarks into hadrons is presented in the framework of the recently developed NJL-jet model, where the momentum and isospin sum rules are satisfied naturally. We present the results for pion, kaon and nucleon fragmentation functions, and compare the results with the empirical functions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

In-Medium QCD Sum Rules for {rho}-Meson and Chiral Scale

In this talk, chiral scale, 4{pi}f{sub {pi}{approx}1} GeV, was introduced as an indicator of partial restoration of chiral symmetry at finite density or temperature, rather than the argument between mass shift and collisional broadening. We use the finite energy sum rules to determine the chiral scale identified with the separation scale of the low-energy resonance part from the high-energy continuum part of {rho}-meson spectral function. In this framework, in-medium {rho}-meson mass should be discussed in terms of the first two moments of the spectral function.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Photoproduction of {pi}{pi} Pairs off {sup 7}Li

This paper reports on the quasi-free photoproduction of {pi}{sup 0}{pi}{sup 0} and {pi}{sup 0}{pi}{sup +/-} pairs from {sup 7}Li in view of the in-medium properties of hadrons. Measurements have been done using the CB/TAPS detector setup and the Glasgow photon tagging spectrometer for incident photon energies up to 820 MeV. At small invariant masses, an enhancement of the neutral invariant mass distributions is seen compared to the mixed charged channel and could be explained either by an in-medium modification of the {pi}{pi} interaction in the I = J = 0 channel or by effects related to the final state interactions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

QCD Phase Diagram at Finite Baryon and Isospin Chemical Potentials

The phase structure of two-flavor QCD is explored for finite temperature T and finite baryon- and isospin-chemical potentials, {mu}{sub B} and {mu}{sub I}, by using the Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model. The PNJL model with the scalar-type eight-quark interaction can reproduce lattice QCD data in the {mu}{sub I}-T plane at {mu}{sub B} = 0. In the {mu}{sub I}-{mu}{sub B}-T space, the critical endpoint of the chiral phase transition in the {mu}{sub B}-T plane at {mu}{sub I} = 0 moves to the tricritical point of the pion-superfluidity phase transition in the {mu}{sub I}-T plane at {mu}{sub B} = 0 as {mu}{sub I} increases.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Extended Brueckner-Hartree-Fock Theory with Pionic Correlation and Chiral Symmetry

We present a nuclear many-body theory with explicit treatment of strong tensor correlation induced by the pion-exchange interaction. For this purpose, the Hartree-Fock variational model space is extended to include 2-particle 2-hole (2p-2h) states, which are able to handle the tensor correlation with high momentum components originating from pseudo-scalar nature of the pion. We take a variational principle of the total energy, and obtain an extended Brueckner-Hartree-Fock equation with inclusion of the effect of the pion exchange and short-range repulsive interaction. This framework has a similar structure as the Brueckner theory and we call this framework extended Brueckner-Hartree-Fock theory.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Extended Chiral ({sigma},{pi},{omega}) Mean-Field Model with Vacuum Fluctuation Corrections

Density-dependent relations among saturation properties of symmetric nuclear matter and properties of hadronic stars are discussed by applying the conserving chiral nonlinear ({sigma},{pi},{omega}) mean-field theory. The chiral nonlinear ({sigma},{pi},{omega}) mean-field theory is an extension of the conserving nonlinear (nonchiral){sigma}-{omega} mean-field theory, which is thermodynamically consistent, relativistic and Lorentz-covariant. In the extended chiral ({sigma},{pi},{omega}) mean-field model, all the masses of hadrons are produced by the spontaneous chiral symmetry breaking, which is different from conventional chiral partner models. By comparing both nonchiral and chiral mean-field approximations, the effects of the chiral symmetry breaking mechanism on the mass of {sigma}-meson, coefficients of nonlinear interactions and Fermi-liquid properties are investigated in nuclear matter and neutron stars.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Extended chiral Hartree-Fock model for nuclear matter

We study the properties of nuclear matter with extended chiral Hartree-Fock model. The two-particle-two-hole (2p-2h) states are introduced in the nucleon ground wave function to take the tensor components of pion into account. We also consider the form factor effect of pion to regularize its high momentum behavior. We find that the pion contribution from 2p-2h states plays a very important role in the saturation mechanism of nuclear matter. Furthermore, the saturation properties are also influenced by the cut-off moment of form factor.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Nucleon Properties in Nuclear Matter

We present recent studies on the effective mass of the nucleon in infinite and homogeneous nuclear matter and its relation to nuclear matter properties within the framework of the in-medium modified Skyrme model. Medium modifications are achieved by introducing optical potential for pion fields and parametrization of the Skyrme parameter in nuclear medium. The present approach is phenomenologically well justified by pion physics in nuclear matter and describe successfully bulk nuclear matter properties.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

pp{yields}p{Lambda}K{sup +} reaction in search for the K{sup -}pp state - quest for a kaonic nuclei

The dibaryonic kaonic nuclear bound state, K{sup -}pp is searched by studying an exclusive p+p{yields}p+{Lambda}+K{sup +} process at several beam energies. A signature of the K{sup -}pp is explored in a p+p{yields}X({identical_to}K{sup -}pp)+K{sup +} reaction that follows a decay of the X into p+{Lambda}. We found in a missing-mass {Delta}M(K{sup +}) spectrum and a {Lambda}p invariant-mass M({Lambda}p) spectrum of DISTO data at 2.85 GeV a resonance with M = 2267 MeV/c{sup 2} and {Gamma} = 118 MeV. Those events are found to be associated with a mono energetic kaon. We investigate this resonance as a candidate of the K{sup -}pp further also with a different beam energies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Studies of antikaon interactions with nucleons at DA{Phi}NE

AMADEUS is an experiment planned to be performed at the DAFNE e{sup +}e{sup -} collider of the Frascati National Laboratories (Italy) of INFN, to investigate the antikaon-nuclei interaction at low energies. AMADEUS will perform, for the first time, full-acceptance studies of antikaon interaction in light nuclei, including a complete experimental program for the case of the kaonic clusters. The study of the absorption of antikaon by the nucleus will provide information concerning the K-barN interaction and the modification of the kaon mass in the nuclear medium.The experiment is being preceded by the study of the hadronic interactions of K{sup -} in the {sup 4}He of the drift chamber from the KLOE experiment data.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2011

Experimental studies on kaonic atoms at DA{Phi}NE

We have measured the K-series x-rays of kaonic hydrogen atoms to determine the strong-interaction energy-level shift and width of the 1s atomic state with significant improvements over the previous experiments. The measurement offers a unique possibility to precisely determine the complex K{sup -}p S-wave scattering length. We have also measured kaonic x-ray spectra with several gaseous targets : deuterium, helium-3 and helium-4. In this paper, we present an overview of this experiment and preliminary spectra of those kaonic x-rays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Precision Spectroscopy of Kaonic Helium-3 X-rays at J-PARC

We will measure the x-rays from kaonic {sup 3}He and {sup 4}He 3d{yields}2p transition by using silicon drift detectors. Our precision goal is set to 1 eV to provide crucial information on the kaon-nucleus strong interaction in the low energy limit. The experiment is to be performed as one of the first experiment in the J-PARC hadron facility (J-PARC E17). An overview and the present status of the experiment are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

A Search for deeply-bound Kaonic nuclear state at the J-PARC E15 experiment

The J-PARC E15 experiment will be performed to search for the simplest kaonic nuclear bound state, K-barNN, by the in-flight {sup 3}He(K{sup -},N) reaction. The exclusive measurement can be performed by a simultaneous measurement of the missing mass using the primary neutron or proton, and the invariant mass via the expected decay, e.g. K{sup -}pp{yields}{Lambda}p{yields}p{pi}{sup -}p. an overview of the experiment and the preparation status are reported.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Application of coupled-channel Complex Scaling Method to {Lambda}(1405)

We have applied the coupled-channel Complex Scaling Method (ccCSM) to the excited baryon {Lambda}(1405) which is the important building block of kaonic nuclei. {Lambda}(1405) is treated as a resonant state of the meson-baryon coupled system, K-barN and {pi}{Sigma}. In this article, it is reported that the ccCSM works well even with an energy-dependent K-barN potential such as a chiral SU(3)-based potential. We have tested two cases: the self-consistency condition is imposed on I) real energy and II) complex energy. Then, the self-consistent solutions are obtained in both cases in the framework of the ccCSM.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Probing internal structure of {Lambda}(1405) in meson-baryon dynamics with chiral symmetry

The internal structure of the resonant {Lambda}(1405) state is investigated based on meson-baryon coupled-channels chiral dynamics, by evaluating density distributions obtained from the form factors of the {Lambda}(1405) state. The form factors are extracted from current-coupled scattering amplitudes in which the current is coupled to the constituent hadrons inside {Lambda}(1405). Using several probe interactions and channel decomposition, we find that the resonant {Lambda}(1405) state is dominantly composed of widely spread K-bar around N, with a small fraction of the escaping {pi}{Sigma} component.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗