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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 OSTI2011

Neutral Current Elastic Interactions in MiniBooNE

Neutral Current Elastic (NCE) interactions in MiniBooNE are discussed. In the neutrino mode MiniBooNE reported: the flux averaged NCE differential cross section as a function of four-momentum transferred squared, an axial mass (M{sub A}) measurement, and a measurement of the strange quark spin content of the nucleon, {Delta}s. In the antineutrino mode we present the background-subtracted data which is compared with the Monte Carlo predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

PWA prospects for K+Lambda and K+Sigma^0 photoproduction

We present a status update on the CMU group PWA efforts in the strangeness (K{sup +}{Lambda}/K{sup +}{Sigma}{sup 0}) sector. The bulk of the currently available data comes from recently published CLAS g11a results, with extensive polarization data expected soon from the CLAS g8 and g9 set of experiments. We give a brief description of issues pertaining to different sign conventions for the polarization observables in the literature, and normalization discrepancies between the CLAS-g11a results and older high energy data from SLAC/CEA/DESY that used an untagged photon beam.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

K*(892) 0 Λ & Κ + Σ*(1385)⁻ photoproduction on the deuteron

Preliminary measurements of the differential cross sections of the γn→Κ*(892)⁰Λ and γn→Κ⁺Σ*(1385)⁻ reactions are shown using data from the Jefferson Lab Hall B CLAS g13 experiment. No experimental cross section data have yet been published on the γn→Κ*(892)⁰Λ reaction, and the only published cross section data on the γn→Κ⁺Σ*(1385)⁻ reaction are at forward angles, where t-channel K⁺ and K* + exchanges are predicted to dominate. These data can be used to contribute to the search for the 'missing' N* resonances, some of which are predicted to have non-negligible couplings to the excited strangeness channels.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Non-perturbative aspects of hadron structure in QCD

We review recent developments in the understanding of hadron structure in the context of QCD. These developments build on the success of lattice QCD and discoveries in chiral perturbation theory. We focus particularly on tests of QCD through the strangeness content of the nucleon, the investigation of excited states of the nucleon, where lattice QCD, experiment and phenomenology meet. Lastly, we discuss the implications of these developments in hadron structure for our understanding of nuclear structure and the equation of state of dense matter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

New thermal model with distinct freeze-out temperatures for baryons and mesons

A significant amount of experimental data for particle production in high-energy heavy ion collisions (10 - 200 GeV/A at center of mass) has been accumulated during last years. Many different theoretical attempts have tried to describe these data using thermal models in the approximation of global thermal equilibrium considering only one freeze-out temperature. However the thermal models often are not able to describe adequately the whole multiplicities of hadrons. For instance, the abundance of strange particles is overestimate and the pion yields are underestimated. In this work is presented a thermal hadronic model with two different temperatures in order to describe the baryonic and mesonic chemical freeze-out in ultra-relativistic heavy ion collisions. The model is used to fit the particle population ratios of the hadrons produced in the reaction. The proposal is not merely to incorporate one additional degree of freedom in the adjustment procedure of data, but to present and alternative scenario for the freeze out stage in the collisional proces s. This new reformulated version of thermal model was applied to a set of data, offering a rather good improvement in the fitting of the calculated particle ratios to the data. The results suggest that the introduced model makes the thermal approach more robust to handle with a larger number of colliding systems and a more comprehensive set of reaction observables.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Charge symmetry breaking and parity violating electron scattering

I review the effects of charge symmetry breaking CSB on electromagnetic form factors and how that influences extraction of information regarding nucleon strangeness content and the weak mixing angle. It seems that CSB effects are very modest and should not impact the analysis of experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Linear resistivity and Sachdev-Ye-Kitaev (SYK) spin liquid behavior in a quantum critical metal with spin-1/2 fermions

Significance In “Planckian metals,” electrons dissipate energy at the fastest possible rate allowed by the fundamental laws of quantum mechanics, resulting in a linear temperature dependence of their electrical resistivity. Although observed for a number of quantum materials, this phenomenon lacks a general theoretical understanding and is often considered as one of the prominent fundamental questions in condensed matter physics. Here, we show that Planckian dissipation and a behavior consistent with the “marginal Fermi liquid” phenomenology emerge in the quantum critical regime separating a Mott insulating spin glass and a Fermi liquid. By establishing this behavior in an explicit model solvable by state-of-the-art computational methods, our theory paves the way toward a deeper understanding of Planckian or “strange” metals.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Hypertriton and light nuclei production at Lambda-production subthreshold energy in heavy-ion collisions

High-energy heavy-ion collisions produce abundant hyperons and nucleons. A dynamical coalescence model coupled with the ART model is employed to study the production probabilities of light clusters, deuteron (d), triton (t), helion ({sup 3}He), and hypertriton ({sub {Lambda}}{sup 3}H) at subthreshold energy of Aproduction ({approx} 1 GeV per nucleon). We study the dependence on the reaction system size of the coalescence penalty factor per additional nucleon and entropy per nucleon. The Strangeness Population Factor (S{sub 3} = {sup 3}{sub {Lambda}}H/({sup 3}He x {Lambda}/p)) shows an extra suppression of hypertriton comparing to light clusters of the same mass number. This model predicts a hypertriton production cross-section of a few {mu}b in {sup 36}Ar+{sup 36}Ar, {sup 40}Ca+{sup 40}Ca and {sup 56}Ni+{sup 56}Ni in 1 A GeV reactions. The production rate is as high as a few hypertritons per million collisions, which shows that the fixed-target heavy-ion collisions at CSR (Lanzhou/China) at {Lambda} subthreshold energy are suitable for breaking new ground in hypernuclear physics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Beam-recoil transferred polarization in $K^+Y$ electroproduction in the nucleon resonance region with CLAS12

We report beam-recoil transferred polarizations for the exclusive electroproduction of K + Λ and K + Σ 0 final states from an unpolarized proton target have been measured using the CLAS12 spectrometer at Jefferson Laboratory. The measurements at beam energies of 6.535 and 7.546 GeV span the range of four-momentum transfer Q 2 from 0.3 to 4.5 GeV 2 and invariant energy W from 1.6 to 2.4 GeV, while covering the full center-of-mass angular range of the K + . These new data extend the existing hyperon polarization data from CLAS in a similar kinematic range but from a significantly larger dataset. They represent an important addition to the world data, allowing for better exploration of the reaction mechanism in strangeness production processes, for further understanding of the spectrum and structure of excited nucleon states, and for improved insight into the strong interaction in the regime of nonperturbative dynamics.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Dynamically generated N* and {Lambda}* resonances in the hidden charm sector around 4.3 GeV

The interactions of D-bar{Sigma}{sub c}-D-bar{Lambda}{sub c}, D-bar*{Sigma}{sub c}-D-bar*{Lambda}{sub c}, and related strangeness channels, are studied within the framework of the coupled-channel unitary approach with the local hidden gauge formalism. A series of meson-baryon dynamically generated relatively narrow N* and {Lambda}* resonances are predicted around 4.3 GeV in the hidden charm sector. We make estimates of production cross sections of these predicted resonances in p-barp collisions for the experiment of antiproton annihilation at Darmstadt (PANDA) at the forthcoming GSI Facility for Antiproton and Ion Research (FAIR) facility.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Neutrino neutral-current elastic scattering on {sup 12}C

The neutral-current elastic scattering of neutrinos on carbon and CH{sub 2} targets is computed using the relativistic distorted-wave impulse approximation with a relativistic optical potential. Results for exclusive and inclusive neutrino reactions on a {sup 12}C target are presented. We show that the nuclear effects on the shape of the four-momentum transferred squared distribution d{sigma}/dQ{sub QE}{sup 2} in neutrino neutral-current and charged-current quasielastic scattering are similar. We also calculate the flux-averaged neutral-current elastic differential cross section d{sigma}/dQ{sub QE}{sup 2} for neutrino scattering from CH{sub 2}, as well as the neutral-current to charged-current cross section ratio as functions of Q{sub QE}{sup 2}. The axial mass M{sub A} is extracted from a fit of the d{sigma}/dQ{sub QE}{sup 2} cross section measured in the MiniBooNE experiment. The extracted value of M{sub A}=1.28{+-}0.05 GeV is consistent within errors with the MiniBooNE result. Additionally, for proton kinetic energies above the Cherenkov threshold, the strange-quark contribution to the neutral-current axial vector form factor at Q{sub QE}{sup 2}=0, {Delta}s, was extracted from a fit to MiniBooNE data for the {nu}p{yields}{nu}p to {nu}N{yields}{nu}N cross section ratio. This value is found to be {Delta}s=-0.11{+-}0.36

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Dressed Polyakov loop and flavor dependent phase transitions

The chiral condensate and dressed Polyakov loop at finite temperature and density have been investigated in the framework of the N{sub f}=2+1 Nambu-Jona-Lasinio (NJL) model with two degenerate u, d quarks and one strange quark. In the case of explicit chiral symmetry breaking with physical quark masses, it is found that the phase transitions for light u, d, and s quark are sequentially happened, and the separation between the transition lines for different flavors becomes wider and wider with the increase of baryon density. For each flavor, the pseudocritical temperatures for chiral condensate and dressed Polyakov loop differ in a narrow transition range in the lower baryon density region, and the two transitions coincide in the higher baryon density region.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Finite-volume effects on octet-baryon masses in covariant baryon chiral perturbation theory

We study finite-volume effects on the masses of the ground-state octet baryons using covariant baryon chiral perturbation theory (ChPT) up to next-to-leading order by analyzing the latest n{sub f}=2+1 lattice quantum chromodynamics (LQCD) results from the NPLQCD Collaboration. Contributions of virtual decuplet baryons are taken into account using the consistent coupling scheme. We compare our results with those obtained from heavy baryon ChPT and show that, although both approaches can describe well the lattice data, the underlying physics is different: In heavy baryon ChPT, virtual decuplet baryons play a more important role than they do in covariant ChPT. This is because the virtual octet-baryon contributions to finite-volume corrections are larger in covariant ChPT than in heavy baryon ChPT, while the contributions of intermediate decuplet baryons are smaller, because of relativistic effects. We observe that for the octet-baryon masses, at fixed m{sub {pi}}L (>>1) finite-volume corrections decrease as m{sub {pi}} approaches its physical value, provided that the strange quark mass is at or close to its physical value, as in most lattice quantum chromodynamics setups.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Quark-mass dependence of the three-flavor QCD phase diagram at zero and imaginary chemical potential: Model prediction

We draw the three-flavor phase diagram as a function of light- and strange-quark masses for both zero and imaginary quark-number chemical potential, using the Polyakov-loop extended Nambu-Jona-Lasinio model with an effective four-quark vertex depending on the Polyakov loop. The model prediction is qualitatively consistent with 2+1 flavor lattice QCD prediction at zero chemical potential and with degenerate three-flavor lattice QCD prediction at imaginary chemical potential.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Updating the neutron electric dipole moment in a fourth generation standard model

A fourth generation of quarks, if it exists, may provide sufficient CP violation for the baryon asymmetry of the Universe. We estimate the neutron electric dipole moment in the presence of a fourth generation and find it would be dominated by the strange quark chromoelectric dipole moment, assuming it does not get wiped out by a Peccei-Quinn symmetry. Both the three electroweak loop and the two-loop electroweak/one-loop gluonic contributions are considered. With m{sub b'}, m{sub t'} at 500 GeV or so that can be covered at the LHC, and with a Jarlskog CP violation factor that is consistent with hints of New Physics in b{yields}s transitions, the neutron electric dipole moment is found around 10{sup -31}e cm, still far below the 10{sup -28}e cm reach of the new experiments being planned or under construction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Recent thermodynamic results from lattice QCD analyzed within a quasiparticle model

The thermodynamic behavior of QCD matter at high temperature is currently studied by lattice QCD theory. The main features are the fast rise of the energy density {epsilon} around the critical temperature T{sub c} and the large trace anomaly of the energy momentum tensor <{Theta}{sub {mu}}{sup {mu}}>={epsilon}-3P, which hints at a strongly interacting system. Such features can be accounted for by employing a massive quasiparticle model with a temperature-dependent bag constant. Recent lattice QCD calculations with physical quark masses by the Wuppertal-Budapest group show a slower increase of {epsilon} and a smaller <{Theta}{sub {mu}}{sup {mu}}> peak with respect to previous results from the HotQCD Collaboration. We investigate the implications of such differences from the point of view of a quasiparticle model, also discussing light and strange quark number susceptibilities. Furthermore, we predict the impact of these discrepancies on the temperature dependence of the transport properties of matter, like the shear and bulk viscosities.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Study of Pion Transverse Momentum Distributions in Ultra-Relativistic Heavy Ion Collisions: A USTFM Approach

The mid-rapidity (|y| < 0.5) transverse momentum distributions of identified charged pions produced in different collision systems at different centre-of-mass energies (√S{sub NN}) ranging from RHIC to LHC have been studied using our early proposed unified statistical thermal freeze-out model (USTFM). We have also studied the effect of different collision centralities on the mid-rapidity (|y| < 0.5) production of pions. Our model results are found to be in good agreement with the experimental data. Different thermal freeze-out conditions which include transverse flow, thermal freeze-out temperature, and velocity profile have been extracted by providing the best fit to the experimental data points. We have incorporated the effects of transverse as well as longitudinal flow in this analysis. The effects of heavier decay resonances are also taken into account. Moreover, the strangeness conservation criteria have also been imposed in this analysis of pion distributions. The calculated freeze-out parameters indicates that the freeze-out temperature increases with decreasing centrality, while the transverse flow velocity increases by increase in the centrality of the colliding system.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗