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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Collective excitations in optical spectra of nanosize exciton and electron-positron droplets

We study the optical properties of nanosize two-component Fermi systems. The photoabsorption spectra in Fermi systems containing not more than 10{sup 2} pairs of oppositely charged particles are calculated. The main focus is on the role of collective plasmon excitations. The dependences of the position of the plasmon resonance on the number of particles and the ratio of their masses in the system are investigated.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Compilation and analysis of charge asymmetry measurements from electron and positron scattering on nucleon and nuclei

World data on the lepton-charge asymmetry in the elastic and inelastic lepton scattering off the proton and nuclei are compiled and discussed. After reviewing the published results, we compare the elastic data to a model calculation of the two-photon-exchange mechanism. We show that the existing data do not provide any evidence for enhancement of the two-photon contribution. At confidence level 95% the data allow to exclude the two-photon exchange as an explanation for the difference between Rosenbluth and polarization transfer measurements of proton electromagnetic form factors.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

New results of measurement of cross sections for electron-positron annihilation to hadrons with the SND detector at VEPP-2000

A survey of preliminary results of experiments with the SND detector at the VEPP-2000 e{sup +}e{sup −} collider in the energy range of √s = 1000–2000 MeV MeV is presented. The cross sections for the processes e{sup +}e{sup −} → π{sup 0}π{sup 0}γ, e{sup +}e{sup −} → π{sup +}π{sup −}π{sup 0}π{sup 0}, e{sup +}e{sup −} → π{sup +}π{sup −}π{sup 0}, e{sup +}e{sup −} → π{sup +}π{sup −}η, and e{sup +}e{sup −} → pp̄ were measured. The measured cross sections agree with the results of earlier measurements but have a higher precision. The cross section for the process e{sup +}e{sup −} → ηγ in the energy range extending from 1.4 to 2 GeV was measured for the first time. The ratio G{sub E}/G{sub M} for the neutron was measured for the first time in the timelike region.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Study of strange charmed baryons in electron–positron collisions

A modern classification of charmed baryons is presented, and the quark model is briefly described for the ground states and energy levels of excited states. In addition, a survey of experimentally observed states of strange charmed baryons is given.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Steady states of a diode with counterstreaming electron and positron beams

Steady states of a plasma layer with counterstreaming beams of oppositely charged particles moving without collisions in a self-consistent electric field are analyzed. The study is aimed at clarifying the mechanism of generation and reconstruction of pulsar radiation. Such a layer also models the processes occurring in Knudsen plasma diodes with counterstreaming electron and ion beams. The steady-state solutions are exhaustively classified. The existence of several solutions at the same external parameters is established.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Joint thrust and TMD resummation in electron-positron and electron-proton collisions

In this work, we present the framework for obtaining precise predictions for the transverse momentum of hadrons with respect to the thrust axis in e + e - collisions. This will enable a precise extraction of transverse momentum dependent (TMD) fragmentation functions from a recent measurement by the Belle Collaboration. Our analysis takes into account, for the first time, the nontrivial interplay between the hadron transverse momentum and the cut on the thrust event shape. To this end, we identify three different kinematic regions, derive the corresponding factorization theorems within Soft Collinear Effective Theory, and present all ingredients needed for the joint resummation of the transverse momentum and thrust spectrum at NNLL accuracy. One kinematic region can give rise to non-global logarithms (NGLs), and we describe how to include the leading NGLs. We also discuss alternative measurements in e + e - collisions that can be used to access the TMD fragmentation function. Finally, by using crossing symmetry, we obtain a new way to constrain TMD parton distributions, by measuring the displacement of the thrust axis in ep collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗