6,543 research outputs found
Propagation of axions in a strongly magnetized medium
The polarization operator of an axion in a degenerate gas of electrons
occupying the ground-state Landau level in a superstrong magnetic field G is investigated in a model with a
tree-level axion-electron coupling. It is shown that a dynamic axion mass,
which can fall within the allowed range of values , is generated under the conditions of strongly
magnetized neutron stars. As a result, the dispersion relation for axions is
appreciably different from that in a vacuum.Comment: RevTex, no figures, 13 pages, Revised version of the paper published
in J. Exp. Theor. Phys. {\bf 88}, 1 (1999
Neutrino dispersion in external magnetic fields
We calculate the neutrino self-energy operator Sigma (p) in the presence of a
magnetic field B. In particular, we consider the weak-field limit e B <<
m_\ell^2, where m_\ell is the charged-lepton mass corresponding to the neutrino
flavor \nu_\ell, and we consider a "moderate field" m_\ell^2 << e B << m_W^2.
Our results differ substantially from the previous literature. For a moderate
field, we show that it is crucial to include the contributions from all Landau
levels of the intermediate charged lepton, not just the ground-state. For the
conditions of the early universe where the background medium consists of a
charge-symmetric plasma, the pure B-field contribution to the neutrino
dispersion relation is proportional to (e B)^2 and thus comparable to the
contribution of the magnetized plasma.Comment: 9 pages, 1 figure, revtex. Version to appear in Phys. Rev. D
(presentation improved, reference list revised, numerical error in Eq.(41)
corrected, conclusions unchanged
Rare semileptonic meson decays in R-parity violating MSSM
We discuss rare meson decays and () in a supersymmetric
extension of the Standard Model with R-parity violation. Estimates of the
branching ratios for these decays are presented.Comment: 5 pages, 1 figure; title modified to better reflect the contents, a
normalization error corrected for D-meson decays, modifying parts of Table 1;
a reference and DESY Report number added; to appear in the Proceedings of the
12th. Lomonosov Conference on Elementary Particle Physics, Moscow State
University, Moscow, Russia, 25-31 August 200
Effects of heavy Majorana neutrinos at lepton-proton colliders
We discuss the prospects of detecting the processes
and
() under the conditions of the present collider
HERA and of future colliders. These high-energy processes are assumed to be
mediated by the exchange of heavy Majorana neutrinos (HMN). We consider two
simple scenarios for the HMN mass spectrum: the effective singlet () and the effective doublet (). For the latter
case, the cross section includes information about CP-violating phases.Comment: 5pages, 2 figures; published in conference proceedings: Particle
Physics in Laboratory, Space and Universe, 11th. Lomonosov Conf. on
Elementary Particle Physics (Moscow, 21-27 August 2003) (Singapore, World
Scientific, 2005
Bilinear R-parity Violation in Rare Meson Decays
We discuss rare meson decays and () in a supersymmetric
extension of the standard model with explicit breaking of R-parity by bilinear
Yukawa couplings in the superpotential. Estimates of the branching ratios for
these decays are given. We also compare our numerical results with analogous
ones previously obtained for two other mechanisms of lepton number violation:
exchange by massive Majorana neutrinos and trilinear R-parity violation.Comment: 5 pages, 1 figure; To appear in the Proceedings of the 13th Lomonosov
Conference on Elementary Particle Physics, 23 -- 29 August, 2007, Moscow,
Russi
Lepton pair production by high-energy neutrino in an external electromagnetic field
The process of the lepton pair production by a neutrino propagating in an
external electromagnetic field is investigated in the framework of the Standard
Model. Relatively simple exact expression for the probability as the single
integral is obtained, which is suitable for a quantitative analysis.Comment: 9 pages, LATEX, 2 PS figures, submitted to Modern Physics Letters
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