1,979 research outputs found
Supernova Bounds on keV-mass Sterile Neutrinos
Sterile neutrinos of keV masses are one of the most promising candidates for
the warm dark matter, which could solve the small-scale problems encountered in
the scenario of cold dark matter. We present a detailed study of the production
of such sterile neutrinos in a supernova core, and derive stringent bounds on
the active-sterile neutrino mixing angles and sterile neutrino masses based on
the standard energy-loss argument.Comment: 10 pages, 2 figures, to be published in the Proceedings of
International Conference on Massive Neutrinos, Singapore, February 9-13,
2015. arXiv admin note: text overlap with arXiv:1109.318
Extrinsic and Intrinsic CPT Asymmetries in Neutrino Oscillations
We reconsider the extrinsic and possible intrinsic CPT violation in neutrino
oscillations, and point out an identity, i.e., , among the CP, T, and
CPT asymmetries in oscillations. For three-flavor oscillations in matter of
constant density, the extrinsic CPT asymmetries , , , and caused by
Earth matter effects have been calculated in the plane of different neutrino
energies and baseline lengths. It is found that two analytical conditions can
be implemented to describe the main structure of the contours of vanishing
extrinsic CPT asymmetries. Finally, without assuming intrinsic CPT symmetry in
the neutrino sector, we investigate the possibility to constrain the difference
of the neutrino CP-violating phase and the antineutrino one
using a low-energy neutrino factory and the super-beam
experiment ESSSB. We find that in the former case and
in the latter case can be achieved at the confidence level if is assumed.Comment: 26 pages, 6 figures, more discussions added, matches the published
versio
Relic Right-handed Dirac Neutrinos and Implications for Detection of Cosmic Neutrino Background
It remains to be determined experimentally if massive neutrinos are Majorana
or Dirac particles. In this connection, it has been recently suggested that the
detection of cosmic neutrino background of left-handed neutrinos and right-handed antineutrinos in future
experiments of neutrino capture on beta-decaying nuclei (e.g., for the PTOLEMY experiment) is likely to
distinguish between Majorana and Dirac neutrinos, since the capture rate is
twice larger in the former case. In this paper, we investigate the possible
impact of right-handed neutrinos on the capture rate, assuming that massive
neutrinos are Dirac particles and both right-handed neutrinos
and left-handed antineutrinos can be efficiently
produced in the early Universe. It turns out that the capture rate can be
enhanced at most by due to the presence of relic and
with a total number density of ,
which should be compared to the number density of cosmic
neutrino background. The enhancement has actually been limited by the latest
cosmological and astrophysical bounds on the effective number of neutrino
generations at the confidence
level. For illustration, two possible scenarios have been proposed for thermal
production of right-handed neutrinos in the early Universe.Comment: 16 pages, 4 figure, more discussions added, references updated, to
appear in Nucl. Phys.
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