32,467 research outputs found
Quantum electrodynamics corrections to energies, transition amplitudes and parity nonconservation in Rb, Cs, Ba, Tl, Fr and Ra
We use previously developed radiative potential method to calculate quantum
electrodynamic (QED) corrections to energy levels and electric dipole
transition amplitudes for atoms which are used for the study of the parity
non-conservation (PNC) in atoms. The QED shift in energies and dipole
amplitudes leads to noticeable change in the PNC amplitudes. This study
compliments the previously considered QED corrections to the weak matrix
elements. We demonstrate that the QED corrections due to the change in energies
and dipole matrix elements are comparable in value to those due to change in
weak matrix elements.Comment: 5 pages, 1 figur
Double core polarization contribution to atomic PNC and EDM calculations
We present a detailed study of the effect of the double core polarization
(the polarization of the core electrons due to the simultaneous action of the
electric dipole and parity-violating weak fields) for amplitudes of the s-s and
s-d parity non-conserving transitions in Rb, Cs, Ba +, La 2+, Tl, Fr, Ra +, Ac
2+ and Th 3+ as well as electron EDM enhancement factors for the ground states
of the above neutral atoms and Au. This effect is quite large and has the
potential to resolve some disagreement between calculations in the literature.
It also has significant consequences for the use of experimental data in the
accuracy analysis.Comment: 6 page
Tectonics and Sedimentation of the Meso- to Neoproterozoic Timan-Varanger Belt along the Northeastern Margin of Baltica
Dark matter scattering on electrons: Accurate calculations of atomic excitations and implications for the DAMA signal
We revisit the WIMP-type dark matter scattering on electrons that results in
atomic ionization, and can manifest itself in a variety of existing
direct-detection experiments. Unlike the WIMP-nucleon scattering, where current
experiments probe typical interaction strengths much smaller than the Fermi
constant, the scattering on electrons requires a much stronger interaction to
be detectable, which in turn requires new light force carriers. We account for
such new forces explicitly, by introducing a mediator particle with scalar or
vector couplings to dark matter and to electrons. We then perform state of the
art numerical calculations of atomic ionization relevant to the existing
experiments. Our goals are to consistently take into account the atomic physics
aspect of the problem (e.g., the relativistic effects, which can be quite
significant), and to scan the parameter space: the dark matter mass, the
mediator mass, and the effective coupling strength, to see if there is any part
of the parameter space that could potentially explain the DAMA modulation
signal. While we find that the modulation fraction of all events with energy
deposition above 2 keV in NaI can be quite significant, reaching ~50%, the
relevant parts of the parameter space are excluded by the XENON10 and XENON100
experiments
On the complexion of pseudoscalar mesons
A strongly momentum-dependent dressed-quark mass function is basic to QCD. It
is central to the appearance of a constituent-quark mass-scale and an
existential prerequisite for Goldstone modes. Dyson-Schwinger equation (DSEs)
studies have long emphasised this importance, and have proved that QCD's
Goldstone modes are the only pseudoscalar mesons to possess a nonzero leptonic
decay constant in the chiral limit when chiral symmetry is dynamically broken,
while the decay constants of their radial excitations vanish. Such features are
readily illustrated using a rainbow-ladder truncation of the DSEs. In this
connection we find (in GeV): f_{eta_c(1S)}= 0.233, m_{eta_c(2S)}=3.42; and
support for interpreting eta(1295), eta(1470) as the first radial excitations
of eta(548), eta'(958), respectively, and K(1460) as the first radial
excitation of the kaon. Moreover, such radial excitations have electromagnetic
diameters greater than 2fm. This exceeds the spatial length of lattices used
typically in contemporary lattice-QCD.Comment: 7 pages, 2 figures. Contribution to the proceedings of the "10th
International Symposium on Meson-Nucleon Physics and the Structure of the
Nucleon (MENU04)," IHEP, Beijing, China, 30/Aug.-4/Sept./0
- …