541 research outputs found
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
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
Turbulent Supernova Shock Waves and the Sterile Neutrino Signature in Megaton Water Detectors
The signatures of sterile neutrinos in the supernova neutrino signal in
megaton water Cerenkov detectors are studied. Time dependent modulation of the
neutrino signal emerging from the sharp changes in the oscillation probability
due to shock waves is shown to be a smoking gun for the existence of sterile
neutrinos. These modulations and indeed the entire neutrino oscillation signal
is found to be different for the case with just three active neutrinos and the
cases where there are additional sterile species mixed with the active
neutrinos. The effect of turbulence is taken into account and it is found that
the effect of the shock waves, while modifed, remain significant and
measurable. Supernova neutrino signals in water detectors can therefore give
unambiguous proof for the existence of sterile neutrinos, the sensitivity
extending beyond that for terrestial neutrino experiments. In addition the time
dependent modulations in the signal due to shock waves can be used to trace the
evolution of the shock wave inside the supernova.Comment: 28 pages, 11 figure
Field-induced axion emission via process in plasma
The annihilation into axion is investigated in a plasma and
an external magnetic field. This process via a plasmon intermediate state has a
resonant character at a particular energy of the emitted axion. The emissivity
by is compared with the axion cyclotron emissivity.Comment: 8 pages, latex, 4 PS figure
Probes of Lorentz Violation in Neutrino Propagation
It has been suggested that the interactions of energetic particles with the
foamy structure of space-time thought to be generated by quantum-gravitational
(QG) effects might violate Lorentz invariance, so that they do not propagate at
a universal speed of light. We consider the limits that may be set on a linear
or quadratic violation of Lorentz invariance in the propagation of energetic
neutrinos, v/c=[1 +- (E/M_\nuQG1)] or [1 +- (E/M_\nu QG2}^2], using data from
supernova explosions and the OPERA long-baseline neutrino experiment. Using the
SN1987a neutrino data from the Kamioka II, IMB and Baksan experiments, we set
the limits M_\nuQG1 > 2.7(2.5)x10^10 GeV for subluminal (superluminal)
propagation, respectively, and M_\nuQG2 >4.6(4.1)x10^4 GeV at the 95%
confidence level. A future galactic supernova at a distance of 10 kpc would
have sensitivity to M_\nuQG1 > 2(4)x10^11 GeV for subluminal (superluminal)
propagation, respectively, and M_\nuQG2 > 2(4)x10^5 GeV. With the current CNGS
extraction spill length of 10.5 micro seconds and with standard clock
synchronization techniques, the sensitivity of the OPERA experiment would reach
M_\nuQG1 ~ 7x10^5 GeV (M_\nuQG2 ~ 8x10^3 GeV) after 5 years of nominal running.
If the time structure of the SPS RF bunches within the extracted CNGS spills
could be exploited, these figures would be significantly improved to M_\nuQG1 ~
5x10^7 GeV (M_\nuQG2 ~ 4x10^4 GeV). These results can be improved further if
similar time resolution can be achieved with neutrino events occurring in the
rock upstream of the OPERA detector: we find potential sensitivities to
M_\nuQG1 ~ 4x10^8 GeV and M_\nuQG2 ~ 7x10^5 GeV.Comment: 33 pages, 22 figures, version accepted for publication in Physical
Review
Oscillations of solar atmosphere neutrinos
The Sun is a source of high energy neutrinos (E > 10 GeV) produced by cosmic
ray interactions in the solar atmosphere. We study the impact of three-flavor
oscillations (in vacuum and in matter) on solar atmosphere neutrinos, and
calculate their observable fluxes at Earth, as well as their event rates in a
kilometer-scale detector in water or ice. We find that peculiar three-flavor
oscillation effects in matter, which can occur in the energy range probed by
solar atmosphere neutrinos, are significantly suppressed by averaging over the
production region and over the neutrino and antineutrino components. In
particular, we find that the relation between the neutrino fluxes at the Sun
and at the Earth can be approximately expressed in terms of phase-averaged
``vacuum'' oscillations, dominated by a single mixing parameter (the angle
theta_23).Comment: v2: 11 pages, 8 eps figures. Content added (Sec. III D and Fig. 6),
references updated. Matches the published versio
Probing non-standard decoherence effects with solar and KamLAND neutrinos
It has been speculated that quantum gravity might induce a "foamy" space-time
structure at small scales, randomly perturbing the propagation phases of
free-streaming particles (such as kaons, neutrons, or neutrinos). Particle
interferometry might then reveal non-standard decoherence effects, in addition
to standard ones (due to, e.g., finite source size and detector resolution.) In
this work we discuss the phenomenology of such non-standard effects in the
propagation of electron neutrinos in the Sun and in the long-baseline reactor
experiment KamLAND, which jointly provide us with the best available probes of
decoherence at neutrino energies E ~ few MeV. In the solar neutrino case, by
means of a perturbative approach, decoherence is shown to modify the standard
(adiabatic) propagation in matter through a calculable damping factor. By
assuming a power-law dependence of decoherence effects in the energy domain
(E^n with n = 0,+/-1,+/-2), theoretical predictions for two-family neutrino
mixing are compared with the data and discussed. We find that neither solar nor
KamLAND data show evidence in favor of non-standard decoherence effects, whose
characteristic parameter gamma_0 can thus be significantly constrained. In the
"Lorentz-invariant" case n=-1, we obtain the upper limit gamma_0<0.78 x 10^-26
GeV at 95% C.L. In the specific case n=-2, the constraints can also be
interpreted as bounds on possible matter density fluctuations in the Sun, which
we improve by a factor of ~ 2 with respect to previous analyses.Comment: Minor changes. Version accepted for publication in Phys. Rev.
Reexamination of a Bound on the Dirac Neutrino Magnetic Moment from the Supernova Neutrino Luminosity
The neutrino helicity-flip process under the conditions of the supernova core
is reinvestigated. Instead of the uniform ball model for the SN core used in
previous analyses, realistic models for radial distributions and time evolution
of physical parameters in the SN core are considered. A new upper bound on the
Dirac neutrino magnetic moment is obtained from the limit on the supernova core
luminosity for nu_R emission.Comment: 13 pages, LaTeX, 8 EPS figures, submitted to Int. J. Mod. Phys.
Field-induced interaction of a pseudoscalar particle with photon in a magnetized plasma
The effective interaction of a pseudoscalar particle with photon in plasma
with the presence of a constant uniform magnetic field is investigated. It is
shown that under some physical conditions the effective coupling between
pseudoscalar particle and photon does not depend on medium parameters and
particles momentum. The probability of the familon decay into photon pair in a
strongly magnetized degenerate ultrarelativistic plasma is calculated.Comment: 10 pages, 2 figures. To be published in Modern Physics Letters
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