822 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
Phase effects in neutrino conversions during a supernova shock wave
Neutrinos escaping from a core collapse supernova a few seconds after bounce
pass through the shock wave, where they may encounter one or more resonances
corresponding to . The neutrino mass eigenstates in
matter may stay coherent between these multiple resonances, giving rise to
oscillations in the survival probabilities of neutrino species. We provide an
analytical approximation to these inevitable phase effects, that relates the
density profile of the shock wave to the oscillation pattern. The phase effects
are present only if the multiple resonances encountered by neutrinos are
semi-adiabatic, which typically happens for 10^{-5} \lsim \sin^2 \theta_{13}
\lsim 10^{-3}. The observability of these oscillations is severely limited by
the inability of the detectors to reconstruct the neutrino energy faithfully.
For typical shock wave profiles, the detection of these phase effects seems
rather unlikely. However, if the effects are indeed identified in the \nuebar
spectra, they would establish inverted hierarchy and a nonzero value of
.Comment: 10 pages, 9 eps figures. Major changes made. Final version to be
published in PR
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
Mass Shift of Axion in Magnetic Field
A mass-shift of the axion propagating in an external constant homogenious
magnetic field is calculated. The contributions via an electron loop and a
virtual photon are examined. It is shown that the virtual photon contribution
dominates substantially over the electron-loop one. Under the conditions of the
early Universe the electron-loop contribution to the massless axion mass-shift
is equal to zero while the virtual photon contribution is finite and can be of
order of the recent restrictions on the axion mass.Comment: 4 pages, latex2e, 2 PS figures, uses ws-p8-50x6-00.sty (included) and
amssymb.sty. Talk at the International Workshop on Particle Physics and the
Early Universe (COSMO-99), Trieste, Italy, 27 September - 3 October 199
Electromagnetic Catalysis of a Neutrino Radiative decay or One More Source of Information on the Lepton Mixing Angles?
The radiative decay of ultrarelativistic massive neutrino is investigated in electromagnetic fields in the framework of the
Standard Model with lepton mixing. Estimates of the decay probability and
``decay cross-section'' for accelerator neutrinos of high energies in the
electric field of nucleus permit one to discuss the general possibility of
carrying out the neutrino experiment. Such an experiment could give unique
information on mixing angles in the lepton sector of the Standard Model which
would be almost independent of the specific neutrino masses.Comment: 6 pages, LaTeX, Talk given by L.A.Vassilevskaya at the XXXth
Rencontres de Moriond, Electroweak Interactions and Unified Theories, Les
Arcs, Savoie, France, March 11-18, 199
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.
(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
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
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