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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 469 records · Page 26
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DOE OSTI2014

Quantum fields with classical perturbations

The main purpose of these notes is a review of various models of Quantum Field Theory (QFT) involving quadratic Lagrangians. We discuss scalar and vector bosons, spin 1/2 fermions, both neutral and charged. Beside free theories, we study their interactions with classical perturbations, called, depending on the context, an external linear source, mass-like term, current or electromagnetic potential. The notes may serve as a first introduction to QFT.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

{Delta}G and {Delta}q-bar measurements at PHENIX

RHIC provides a unique opportunity to address the components of the proton spin. In comparison to deep inelastic scattering experiments, the gluon is the main player in proton-proton collisions. PHENIX has measured double spin asymmetries of various processes. Those contain the information of the gluon spin component ({Delta}G). In addition high energy collisions open the unique channel to access flavor dependent information of quark polarization through the real W boson production. Because of the feature of weak interaction, the parity violating process defines the helicity of quarks in the interaction. The single spin asymmetry is the observable. It is especially interesting to probe anti-quark components ({Delta}q-bar). In this article, we report the recent progress of {Delta}G and {Delta}q-bar measurements at PHENIX.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Model-independent determination of the axial mass parameter in quasielastic neutrino-nucleon scattering

Quasielastic neutrino-nucleon scattering is a basic signal process for neutrino oscillation studies. At accelerator energies, the corresponding cross section is subject to significant uncertainty due to the poorly constrained axial-vector form factor of the nucleon. A model-independent description of the axial-vector form factor is presented. Data from the MiniBooNE experiment for quasielastic neutrino scattering on {sup 12}C are analyzed under the assumption of a definite nuclear model. The value of the axial mass parameter, m{sub A}=0.85{sub -0.07}{sup +0.22}{+-}0.09 GeV, is found to differ significantly from extractions based on traditional form factor models. Implications for future neutrino scattering and pion electroproduction measurements are discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Ab initio no core shell model

A long-standing goal of nuclear theory is to determine the properties of atomic nuclei based on the fundamental interactions among the protons and neutrons (i.e., nucleons). By adopting nucleon-nucleon (NN), three-nucleon (NNN) and higher-nucleon interactions determined from either meson-exchange theory or QCD, with couplings fixed by few-body systems, we preserve the predictive power of nuclear theory. This foundation enables tests of nature's fundamental symmetries and offers new vistas for the full range of complex nuclear phenomena. Basic questions that drive our quest for a microscopic predictive theory of nuclear phenomena include: (1) What controls nuclear saturation; (2) How the nuclear shell model emerges from the underlying theory; (3) What are the properties of nuclei with extreme neutron/proton ratios; (4) Can we predict useful cross sections that cannot be measured; (5) Can nuclei provide precision tests of the fundamental laws of nature; and (6) Under what conditions do we need QCD to describe nuclear structure, among others. Along with other ab initio nuclear theory groups, we have pursued these questions with meson-theoretical NN interactions, such as CD-Bonn and Argonne V18, that were tuned to provide high-quality descriptions of the NN scattering phase shifts and deuteron properties. We then add meson-theoretic NNN interactions such as the Tucson-Melbourne or Urbana IX interactions. More recently, we have adopted realistic NN and NNN interactions with ties to QCD. Chiral perturbation theory within effective field theory ({chi}EFT) provides us with a promising bridge between QCD and hadronic systems. In this approach one works consistently with systems of increasing nucleon number and makes use of the explicit and spontaneous breaking of chiral symmetry to expand the strong interaction in terms of a dimensionless constant, the ratio of a generic small momentum divided by the chiral symmetry breaking scale taken to be about 1 GeV/c. The resulting NN and NNN interactions, characterized by the order of the expansion retained (e.g. 'next-to-next-to leading order' is NNLO), provide a high-quality fit to the NN data and the A = 3 ground-state (g.s.) properties. The derivations of NN, NNN, etc. interactions within meson-exchange and {chi}EFT are well-established but are not subjects of this review. Our focus is solution of the non-relativistic quantum many-body Hamiltonian that includes these interactions using our no core shell model (NCSM) formalism. In the next section we will briefly outline the NCSM formalism and then present applications, results and extensions in later sections.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Renormalization of one meson exchange potentials and their currents

The Nucleon-Nucleon One Meson Exchange Potential, its wave functions and related Meson Exchange Currents are analyzed for point-like nucleons. The leading N{sub c} contributions generate a local and energy independent potential which presents 1/r{sup 3} singularities, requiring renormalization. We show how invoking suitable boundary conditions, neutron-proton phase shifts and deuteron properties become largely insensitive to the nucleon substructure and to the vector mesons. Actually, reasonable agreement with low energy data for realistic values of the coupling constants (e.g. SU(3) values) is found. The analysis along similar lines for the Meson Exchange Currents suggests that this renormalization scheme implies tremendous simplifications while complying with exact gauge invariance at any stage of the calculation.

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 OSTI2022

Exploring the phenomenology of weak adjoint scalars in minimal R -symmetric models

We examine the phenomenology of the scalar fields in weak and Higgs sectors of minimal R-symmetric models, in particular the ‘swino’ and ‘sbino’, the scalar partners to the chiral fields that marry the electroweak gauge bosons in Dirac gaugino models. These fields are in adjoint representations of SU(2) and U(1) and have both CP-even and CP-odd components. The interactions of these new states are summarized, and decay widths are computed analytically to one loop order. We discuss the tree level contributions of these new states to the mass spectrum of MSSM sfermions. We also explore production cross sections and decay signatures at colliders for several chosen benchmarks. We find that large regions of parameter space are unconstrained by present collider data.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Search for long-lived particles decaying to a pair of muons in proton-proton collisions at $ \sqrt{s} $ = 13 TeV

An inclusive search for long-lived exotic particles decaying to a pair of muons is presented. The search uses data collected by the CMS experiment at the CERN LHC in proton-proton collisions at $ \sqrt{s} $ = 13 TeV in 2016 and 2018 and corresponding to an integrated luminosity of 97.6 fb$^{−1}$. The experimental signature is a pair of oppositely charged muons originating from a common secondary vertex spatially separated from the pp interaction point by distances ranging from several hundred μm to several meters. The results are interpreted in the frameworks of the hidden Abelian Higgs model, in which the Higgs boson decays to a pair of long-lived dark photons Z$_{D}$, and of a simplified model, in which long-lived particles are produced in decays of an exotic heavy neutral scalar boson. For the hidden Abelian Higgs model with m(Z$_{D}$) greater than 20 GeV and less than half the mass of the Higgs boson, they provide the best limits to date on the branching fraction of the Higgs boson to dark photons for cτ(Z$_{D}$) (varying with m(Z$_{D}$)) between 0.03 and ≈0.5 mm, and above ≈0.5 m. Our results also yield the best constraints on long-lived particles with masses larger than 10 GeV produced in decays of an exotic scalar boson heavier than the Higgs boson and decaying to a pair of muons.[graphic not available: see fulltext]

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Light and heavy at the end of the funnel

We show that, by taking a bare mass spectrum with constant spacings for the quark-antiquark propagators, which is subject to considerable mass shifts from meson loops, one adequately describes a large variety of mesonic resonances, from the light scalars to the bb-bar states. All our results indicate that a harmonic-oscilator spectrum with universal frequency, in combination with coupled-channel effects, does a much better job than the qq-bar spectrum of the funnel potential.

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 OSTI2017

The HPS experiment

With the experimental discovery of the Higgs boson, the Standard Model has been considered veri ed in all its previsions. The Standard Model, though, is still considered an incomplete theory, because it fails to address many theoretical and phenomenological issues. Among those, it doesn't provide any viable Dark Matter candidate. Many Beyond-Standard Model theories, such as the Supersymmetric Standard Model, provide possible solutions. In this work we have reported the experimental observations that led to considerate the existence of a new Force, mediated by a new massive vector boson, that could address all the observed phenomenology. This new dark Force could open an observational channel between the Standard Model and a new Dark Sector, convey by the interaction of the Standard Model photon with the massive dark photon, also called the A'. Purpose of this work was to develop an independent study of the background processes and the implementation of an independent event generator, to better understand the kinematics of the produced particles in the process e - +W → e - +W' + e + + e - and validate, or invalidate, the o cial event generator.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Conformal freeze-in, composite dark photon, and asymmetric reheating

Large classes of dark sector models feature mass scales and couplings very different from the ones we observe in the Standard Model (SM). Moreover, in the freeze-in mechanism, often employed by the dark sector models, it is also required that the dark sector cannot be populated during the reheating process like the SM. This is the so called asymmetric reheating. Such disparities in sizes and scales often call for dynamical explanations. In this paper, we explore a scenario in which slow evolving conformal field theories (CFTs) offer such an explanation. Building on the recent work on conformal freeze-in (COFI), we focus on a coupling between the Standard Model Hypercharge gauge boson and an anti-symmetric tensor operator in the dark CFT. We present a scenario which dynamically realizes the asymmetric reheating and COFI production. With a detailed study of dark matter production, and taking into account limits on the dark matter (DM) self-interaction, warm DM bound, and constraints from the stellar evolution, we demonstrate that the correct relic abundance can be obtained with reasonable choices of parameters. The model predicts the existence of a dark photon as an emergent composite particle, with a small kinetic mixing also determined by the CFT dynamics, which correlates it with the generation of the mass scale of the dark sector. At the same time, COFI production of dark matter is very different from those freeze-in mediated by the dark photon. This is an example of the physics in which a realistic dark sector model can often be much richer and with unexpected features.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Searching for BSM neutrino interactions in dark matter detectors

Neutrino interactions beyond the Standard Model (BSM) are theoretically well motivated and have an important impact on the future precision measurement of neutrino oscillation. In this work, we study the sensitivity of a multi-ton-scale liquid Xenon dark matter detector equipped with an intense radioactive neutrino source to various BSM neutrino-electron interactions. We consider the conventional Non-Standard Interactions (NSIs), other more generalized four-fermion interactions including scalar and tensor forms, and light-boson mediated interactions. The work shows that with realistic experimental setups, one can achieve unprecedented sensitivity to these BSM neutrino-electron interactions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Kaon photoproduction and electroproduction near threshold

We analyze the electromagnetic production of K{sup +}{Lambda} and K{sup 0}{Lambda} near their production thresholds by using isobar models. In the K{sup +}{Lambda} channel we show that the model can nicely describe the available experimental data. In the K{sup 0}{Lambda} channel we demonstrate that the K{sup 0} charge form factor has sizable effects on the longitudinal cross section. By extending the model up to W = 1730 MeV, we are able to observe the existence of the narrow P{sub 11}(J{sup p} = 1/2{sup +}) resonance in the kaon photoproduction process. It is found that the most convincing mass (width) of this resonance is 1650 MeV(5 MeV).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Elastic electron-deuteron scattering in the light-front Hamiltonian dynamics

Within the Light-Front Hamiltonian Dynamics, we are extending our investigation of the deuteron electromagnetic properties by adding new, dynamical two-body terms to the one-body current operator, introduced in previous works. These two-body contributions are generated in a four-dimensional Yukawa model (two fermions interacting through a pion) from an analysis of the Light-Front-projected current that acts on the three-dimensional valence component and fulfills the Ward-Takahashi identity. Preliminary results for the magnetic moment and the non valence probability are shown.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗