647 research outputs found
Adiabatic Faraday effect in a two-level Hamiltonian formalism
The helicity of a photon traversing a magnetized plasma can flip when the
B-field along the trajectory slowly reverses. Broderick and Blandford have
recently shown that this intriguing effect can profoundly change the usual
Faraday effect for radio waves. We study this phenomenon in a formalism
analogous to neutrino flavor oscillations: the evolution is governed by a
Schroedinger equation for a two-level system consisting of the two photon
helicities. Our treatment allows for a transparent physical understanding of
this system and its dynamics. In particular, it allows us to investigate the
nature of transitions at intermediate adiabaticities.Comment: 8 pages, 2 eps figures, and a note added. Title changed. Matches
published versio
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
Inverse problems in diffraction
A two-dimensional problem of diffraction of a plane electromagnetic wave on a smooth 2 pi-periodic surface is considered. A numerical algorithm solving this problem is developed. An inverse problem of determination of the shape of 2 pi-periodic surface using the performance data of reverse scattering is considered. The inverse problem was solved by means of minimization of the residual functional with the help of the gradient descent method. The initial data were calculated with the help of the numerical method. On each step of the iterative method of minimization, the residual functional was calculated approximately with the help of the small slope method. The examples of the shape determination are considered
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
Neutrino Oscillations, Lorentz/CPT Violation, and Dark Energy
If dark energy (DE) couples to neutrinos, then there may be apparent
violations of Lorentz/CPT invariance in neutrino oscillations. The DE-induced
Lorentz/CPT violation takes a specific form that introduces neutrino
oscillations that are energy independent, differ for particles and
antiparticles, and can lead to novel effects for neutrinos propagating through
matter. We show that ultra-high-energy neutrinos may provide one avenue to seek
this type of Lorentz/CPT violation in \nu_\mu-\nu_\tau oscillations, improving
the current sensitivity to such effects by seven orders of magnitude.
Lorentz/CPT violation in electron-neutrino oscillations may be probed with the
zenith-angle dependence for high-energy atmospheric neutrinos. The ``smoking
gun,'' for DE-neutrino coupling would, however, be a dependence of neutrino
oscillations on the direction of the neutrino momentum relative to our peculiar
velocity with respect to the CMB rest frame. While the amplitude of this
directional dependence is expected to be small, it may nevertheless be worth
seeking in current data and may be a target for future neutrino experiments.Comment: 9 pages, 3 figure
(Down-to-)Earth matter effect in supernova neutrinos
Neutrino oscillations in the Earth matter may introduce peculiar modulations
in the supernova (SN) neutrino spectra. The detection of this effect has been
proposed as diagnostic tool for the neutrino mass hierarchy at "large" 1-3
leptonic mixing angle theta13. We perform an updated study on the observability
of this effect at large next-generation underground detectors (i.e., 0.4 Mton
water Cherenkov, 50 kton scintillation and 100 kton liquid Argon detectors)
based on neutrino fluxes from state-of-the-art SN simulations and accounting
for statistical fluctuations via Montecarlo simulations. Since the average
energies predicted by recent simulations are lower than previously expected and
a tendency towards the equalization of the neutrino fluxes appears during the
SN cooling phase, the detection of the Earth matter effect will be more
challenging than expected from previous studies. We find that none of the
proposed detectors shall be able to detect the Earth modulation for the
neutrino signal of a typical galactic SN at 10 kpc. It should be observable in
a 100 kton liquid Argon detector for a SN at few kpc and all three detectors
would clearly see the Earth signature for very close-by stars only (d ~ 0.2
kpc). Finally, we show that adopting IceCube as co-detector together with a
Mton water Cherenkov detector is not a viable option either.Comment: (14 pages, 5 ps figures
What Fraction of Boron-8 Solar Neutrinos arrive at the Earth as a nu_2 mass eigenstate?
We calculate the fraction of B^8 solar neutrinos that arrive at the Earth as
a nu_2 mass eigenstate as a function of the neutrino energy. Weighting this
fraction with the B^8 neutrino energy spectrum and the energy dependence of the
cross section for the charged current interaction on deuteron with a threshold
on the kinetic energy of the recoil electrons of 5.5 MeV, we find that the
integrated weighted fraction of nu_2's to be 91 \pm 2 % at the 95% CL. This
energy weighting procedure corresponds to the charged current response of the
Sudbury Neutrino Observatory (SNO). We have used SNO's current best fit values
for the solar mass squared difference and the mixing angle, obtained by
combining the data from all solar neutrino experiments and the reactor data
from KamLAND. The uncertainty on the nu_2 fraction comes primarily from the
uncertainty on the solar delta m^2 rather than from the uncertainty on the
solar mixing angle or the Standard Solar Model. Similar results for the
Super-Kamiokande experiment are also given. We extend this analysis to three
neutrinos and discuss how to extract the modulus of the Maki-Nakagawa-Sakata
mixing matrix element U_{e2} as well as place a lower bound on the electron
number density in the solar B^8 neutrino production region.Comment: 23 pages, 8 postscript figures, latex. Dedicated to the memory of
John Bahcall who championed solar neutrinos for many lonely year
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
Sensitivity of T2KK to the non-standard interaction in propagation
Assuming only the non-zero electron and tau neutrino components
, , of the non-standard
matter effect and postulating the atmospheric neutrino constraint
, we study the
sensitivity to the non-standard interaction in neutrino propagation of the T2KK
neutrino long-baseline experiment. It is shown that T2KK can constrain the
parameters , . It is
also shown that if and are large, then T2KK
can determine the Dirac phase and the phase of separately,
due to the information at the two baselines. We also provide an argument that
the components must be small for
the disappearance oscillation probability to be consistent with high-energy
atmospheric neutrino data, which justifies our premise that these quantities
are negligible.Comment: 29 pages, 25 figures, uses revtex4-1. Several places including typos
revised. New references adde
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
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