806 research outputs found
Familon emission by dense magnetized plasma
Emission of a familon caused by the processes , in dense magnetized plasma is investigated in the model in which
a familon have both direct and no direct coupling to leptons via plasmon. The
process probabilities and the integral familon action on plasma are calculated.
It is shown that the odd interference phenomenon in the process leads to the familon force acting on plasma along the magnetic
field.Comment: 7 pages, LATEX, to appear in Modern Physics Letters
Neutrino Oscillations as a Probe of Dark Energy
We consider a class of theories in which neutrino masses depend significantly
on environment, as a result of interactions with the dark sector. Such theories
of mass varying neutrinos (MaVaNs) were recently introduced to explain the
origin of the cosmological dark energy density and why its magnitude is
apparently coincidental with that of neutrino mass splittings. In this Letter
we argue that in such theories neutrinos can exhibit different masses in matter
and in vacuum, dramatically affecting neutrino oscillations. Both long and
short baseline experiments are essential to test for these interactions. As an
example of modifications to the standard picture, we consider simple models
which may simultaneously account for the LSND anomaly, KamLAND, K2K and studies
of solar and atmospheric neutrinos, while providing motivation to continue to
search for neutrino oscillations in short baseline experiments such as BooNE.Comment: 5 pages, 1 figure, refs added, additional data considered, minor
change in conclusions about LSN
Effects of CP Violation from Neutral Heavy Fermions on Neutrino Oscillations, and the LSND/MiniBooNE Anomalies
Neutrinos may mix with ultralight fermions, which gives flavor oscillations,
and with heavier fermions, which yields short distance flavor change. I
consider the case where both effects are present. I show that in the limit
where a single oscillation length is experimentally accessible, the effects of
heavier fermions on neutrino oscillations can generically be accounted for by a
simple formula containing four parameters, including observable CP violation. I
consider the anomalous LSND and MiniBooNE results, and show that these can be
fit in a model with CP violation and two additional sterile neutrinos, one in
the mass range between 0.1 and 20 eV, and the other with mass between 33 eV and
40 GeV. I also show that this model can avoid conflict with constraints from
existing null short baseline experimental results.Comment: 12 pages, 3 figure
Oscillations of high energy neutrinos in matter: Precise formalism and parametric resonance
We present a formalism for precise description of oscillation phenomena in
matter at high energies or high densities, V > \Delta m^2/2E, where V is the
matter-induced potential of neutrinos. The accuracy of the approximation is
determined by the quantity \sin^2 2\theta_m \Delta V/2\pi V, where \theta_m is
the mixing angle in matter and \Delta V is a typical change of the potential
over the oscillation length (l \sim 2\pi/V). We derive simple and physically
transparent formulas for the oscillation probabilities, which are valid for
arbitrary matter density profiles. They can be applied to oscillations of high
energy (E > 10 GeV) accelerator, atmospheric and cosmic neutrinos in the matter
of the Earth, substantially simplifying numerical calculations and providing an
insight into the physics of neutrino oscillations in matter. The effect of
parametric enhancement of the oscillations of high energy neutrinos is
considered. Future high statistics experiments can provide an unambiguous
evidence for this effect.Comment: LaTeX, 5 pages, 1 figure. Linestyles in the figure corrected to match
their description in the caption; improved discussion of the accuracy of the
results; references added. Results and conclusions unchange
Neutrino oscillations in a stochastic model for space-time foam
We study decoherence models for flavour oscillations in four-dimensional
stochastically fluctuating space times and discuss briefly the sensitivity of
current neutrino experiments to such models. We pay emphasis on demonstrating
the model dependence of the associated decoherence-induced damping coefficients
in front of the oscillatory terms in the respective transition probabilities
between flavours. Within the context of specific models of foam, involving
point-like D-branes and leading to decoherence-induced damping which is
inversely proportional to the neutrino energies, we also argue that future
limits on the relevant decoherence parameters coming from TeV astrophysical
neutrinos, to be observed in ICE-CUBE, are not far from theoretically expected
values with Planck mass suppression. Ultra high energy neutrinos from Gamma Ray
Bursts at cosmological distances can also exhibit in principle sensitivity to
such effects.Comment: 12 pages RevTex4, no figure
Neutrino-electron processes in a dense maqnetized plasma
The neutrino-electron processes in a dense strongly degenerate magnetized
plasma are analyzed in the framework of the Standard Model. The total
probability and the mean values of the neutrino energy and momentum losses are
calculated. It is shown that neutrino scattering on the excited electrons with
Landau level number conservation dominates under the conditions "mu^2 > eB >>
mu T" but does not give a contribution into the neutrino force acting on plasma
along the magnetic field.Comment: 7 pages, LATEX, to appear in Modern Physics Letters
Fermion dispersion in axion medium
The interaction of a fermion with the dense axion medium is investigated for
the purpose of finding an axion medium effect on the fermion dispersion. It is
shown that axion medium influence on the fermion dispersion under astrophysical
conditions is negligible small if the correct Lagrangian of the axion-fermion
interaction is used.Comment: 5 pages, 1 figure, to appear in International Journal of Modern
Physics
Large Lepton Asymmetry for Small Baryon Asymmetry and Warm Dark Matter
We propose a resonant leptogenesis scenario in a U(1)_{B-L} gauge extension
of the standard model to generate large lepton asymmetries for cosmological
baryon asymmetry and dark matter. After B-L number is spontaneously broken,
inflaton can pick up a small vacuum expectation value for the mass splits of
three pairs of quasi-degenerately heavy Majorana neutrinos and the masses of
three sterile neutrinos. With thermal mass effects of sphalerons, the observed
small baryon asymmetry can be converted from large lepton asymmetries of
individual flavors although total lepton asymmetry is assumed zero. The mixing
between sterile and active neutrinos is elegantly suppressed by the heavy
Majorana neutrinos. Before the active neutrinos start their strong flavor
conversions, the sterile neutrinos as warm dark matter can be produced by
resonant active-sterile neutrino oscillations to reconcile X-ray and
Lyman-\alpha bounds. Small neutrino masses are naturally realized by seesaw
contributions from the heavy Majorana neutrinos and the sterile neutrinos.Comment: 8 pages. Typos and parameter choice are corrected. Accepted by Phys.
Rev.
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