By calculating the radiative corrections to such an annihilation process, we show that the positrons produced would necessarily be accompanied by a flux of (“internal bremsstrahlung”) gamma rays, of sufficient magnitude to exceed the observed galactic diffuse gamma ray flux, unless the dark matter mass is less than about 20 MeV. This motivates the recent suggestion that the positrons are produced instead by the annihilation of light (1-100 MeV) dark matter particles in the Galactic halo. The Galactic positron flux, observed as a 0.511 MeV annihilation line, is difficult to account for with astrophysical sources. Galactic Positrons and Annihilating Dark Matter: For Majorana neutrinos the magnetic moment contribution to the mass term is suppressed by Yukawa couplings, thus we do not exclude the possibility of detecting a magnetic moment experimentally. For Dirac neutrinos we find a bound several orders of magnitude more stringent than present experimental limits. Although neutrinos are electromagnetically neutral (they have no electric charge and no magnetic moment), they may carry another kind of charge: lepton number. Using the new limit on the neutrino magnetic moment recently obtained by the GEMMA experiment on measurements of the reactor antineutrino scattering off. The explicit evalu- ation of the one-loop contributions to the Dirac neutrino magnetic moment in the leading approx- imation over small parameters b i m 2 i M 2 W (m i are the neutrino masses, i 1,2, 3. An antineutrino is the antiparticle partner of the neutrino, meaning that the antineutrino has the same mass but opposite charge of the neutrino. Neutrino magnetic moment in a minimal ex- tension of Standard Model. There- fore, neutrino magnetic moments can be used to distinguish Dirac and Majorana neutrinos (see 3 and also 2 for a detailed discussion). We derive model-independent upper bounds on neutrino magnetic moments generated by physics above the electroweak scale. For a Majorana neutrino the diagonal magnetic and electric moments are zero. However, the existence of a neutrino magnetic moment implies contributions to the neutrino mass via electroweak radiative corrections. The latter relation may also be deduced from a. Alternatively, a magnetic moment for a massive neutrino arising from gravitational origin is predicted by the so-called Wilson-Blackett law. Theoretically, it is possible to account for a neutrino magnetic moment only as the result of the interaction of the electromagnetic field with charged particles into which the neutrino can transform virtually. ![]() A linear dependence on the neutrino mass was found. The detection of a neutrino magnetic moment comparable to present limits would be an unequivocal indication of physics beyond the Standard Model. In 1977 an expression for the magnetic moment of a massive Dirac neutrino was deduced in the context of electroweak interactions at the one-loop level. Neutrino Magnetic Moments/ Galactic Positrons and Annihilating Dark Matter – Nicole Bell Date: Fri.
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