Search results for " DIP"
showing 10 items of 1273 documents
Self-consistency conditions for localized magnetic moments in a free electron gas
1969
The self-consistent conditions for a localized magnetic moment in a metal are studied in the case where the density of states of the host metal is free electron like. A method is outlined which in principle allows to determine self-consistently in the Hartree-Fock approximation the relevant parameters of the magnetic ground state of the system. A numerical example is approximately worked out to show how the theory gives reasonable answers in spite of the crudeness of some of the approximations used.
Hyperfine structure measurements of neutral niobium with Fourier transform spectroscopy
2010
Aims. We report on experimental studies of hyperfine structure splitting of neutral niobium.Methods. We used high-resolution Fourier transform spectroscopy to record a spectrum of niobium produced with a hollow cathode discharge lamp in the range of wavenumbers from 10 000 cm-1 to 30 000 cm-1 .Results. The magnetic dipole hyperfine structure constants A were determined for the 109 levels of odd parity by analyzing the profiles of 224 spectral lines. The A values of 57 of these level are reported for the first time.
Search at the Mainz Microtron for light massive gauge bosons relevant for the muon g-2 anomaly.
2014
A massive, but light, Abelian U(1) gauge boson is a well-motivated possible signature of physics beyond the standard model of particle physics. In this Letter, the search for the signal of such a U(1) gauge boson in electron-positron pair production at the spectrometer setup of the A1 Collaboration at the Mainz Microtron is described. Exclusion limits in the mass range of 40 MeV/c^{2} to 300 MeV/c^{2}, with a sensitivity in the squared mixing parameter of as little as ε^{2}=8×10^{-7} are presented. A large fraction of the parameter space has been excluded where the discrepancy of the measured anomalous magnetic moment of the muon with theory might be explained by an additional U(1) gauge …
Standard model higher order corrections to the WW gamma/WWZ vertex
1995
Using the S--matrix pinch technique we obtain to one loop order gauge independent $\gamma W^-W^+$ and $Z W^-W^+$ vertices in the context of the standard model, with all incoming momenta off--shell. We show that the vertices so constructed satisfy simple QED--like Ward identities. These gauge invariant vertices give rise to expressions for the magnetic dipole and electric quadrupole form factors of the $W$ gauge boson, which, unlike previous treatments, satisfy the crucial properties of infrared finiteness and perturbative unitarity.
The Random-Phase Approximation
2007
In this chapter we extend the TDA particle-hole formalism of Chap. 9 to include correlations in the nuclear ground state. This sophisticated particle-hole formalism is called the random-phase approximation (RPA). In this description the simple Hartree-Fock particle-hole vacuum is replaced by a correlated ground state involving many-particle-many-hole excitations of the simple particle-hole vacuum. The resulting configuration mixing in excited states is more involved in the RPA than it is in the TDA. The ground-state correlations induce both particle-hole and hole-particle components in the RPA wave function.
Alfven QPOs in magnetars in the anelastic approximation
2009
We perform two-dimensional simulations of Alfven oscillations in magnetars, modeled as relativistic stars with a dipolar magnetic field. We use the anelastic approximation to general relativistic magnetohydrodynamics, which allows for an effective suppression of fluid modes and an accurate description of Alfven waves. In addition, we compute Alfven oscillation frequencies along individual magnetic field lines with a semi-analytic approach, employing a short-wavelength approximation. Our main findings are as follows: a) we confirm the existence of two families of quasi-periodic oscillations (QPOs), with harmonics at integer multiples of the fundamental frequency, as was found in the linear s…
Overview of the hadronic light-by-light contribution to the muon (g−2)
2014
In this talk I review the recent progress on the numerical evaluation of the Hadronic Light-by-Light contribution to the anomalous magnetic moment of the muon and I discuss the role of experimental data on the accuracy of its determination.
Evolution of Mixed Dirac Particles Interacting with an External Magnetic Field
2007
We study in the framework of relativistic quantum mechanics the evolution of a system of two Dirac neutrinos that mix with each other and have non-vanishing magnetic moments. The dynamics of this system in an external magnetic field is determined by solving the Pauli-Dirac equation with a given initial condition. We consider first neutrino spin-flavor oscillations in a constant magnetic field and derive an analytical expression for the transition probability of spin-flavor conversion in the limit of small magnetic interactions. We then investigate ultrarelativistic neutrinos in an transversal magnetic field and derive their wave functions and transition probabilities with no limitation for …
WMAPing the Universe: Supersymmetry, Dark Matter, Dark Energy, Proton Decay and Collider Physics
2003
In this review we discuss constraints on minimal supersymmetric models of particle physics implied by the recent astrophysical observations of WMAP. Although the prospects of detecting supersymmetry increase and 90 percent of the available MSSM parameter space can safely be reached by the sensitivity of future colliders, nevertheless we pay particular emphasis on discussing regions of the appropriate phase diagrams, which -if realized - would imply that detection of supersymmetry, at least in the context of minimal models, could be out of colliders reach. We also discuss the importance of a precise determination of the radiative corrections to the muon anomalous magnetic moment, both theore…
Calculation of atomic properties of superheavy elements Z=110–112 and their ions
2020
We calculate the spectra, electric dipole transition rates, and isotope shifts of the superheavy elements Ds ($Z=110$), Rg ($Z=111$), and Cn ($Z=112$) and their ions. These calculations were performed using a recently developed, efficient version of the ab intio configuration-interaction combined with perturbation theory to treat distant effects. The successive ionization potentials of the three elements are also calculated and compared to lighter analogous elements.