5,299 research outputs found
Captures of Hot and Warm Sterile Antineutrino Dark Matter on EC-decaying Ho-163 Nuclei
Capturing low-energy electron antineutrinos on radioactive Ho-163 nuclei,
which decay into Dy-163 via electron capture (EC), is a noteworthy opportunity
to detect relic sterile antineutrinos. Such hypothetical particles are more or
less implied by current experimental and cosmological data, and they might be a
part of hot dark matter or a candidate for warm dark matter in the Universe.
Using the isotope Ho-163 as a target and assuming reasonable active-sterile
antineutrino mixing angles, we calculate the capture rate of relic electron
antineutrinos against the corresponding EC-decay background in the presence of
sterile antineutrinos at the sub-eV or keV mass scale. We show that the
signature of hot or warm sterile antineutrino dark matter should in principle
be observable, provided the target is big enough and the energy resolution is
good enough.Comment: 16 pages, 6 figures, more discussions and references added. To appear
in JCA
Indirect unitarity violation entangled with matter effects in reactor antineutrino oscillations
If finite but tiny masses of the three active neutrinos are generated via the
canonical seesaw mechanism with three heavy sterile neutrinos, the 3\times 3
Pontecorvo-Maki-Nakagawa-Sakata neutrino mixing matrix V will not be exactly
unitary. This kind of indirect unitarity violation can be probed in a precision
reactor antineutrino oscillation experiment, but it may be entangled with
terrestrial matter effects as both of them are very small. We calculate the
probability of \overline{\nu}_e \to \overline{\nu}_e oscillations in a good
analytical approximation, and find that, besides the zero-distance effect, the
effect of unitarity violation is always smaller than matter effects, and their
entanglement does not appear until the next-to-leading-order oscillating terms
are taken into account. Given a 20-kiloton JUNO-like liquid scintillator
detector, we reaffirm that terrestrial matter effects should not be neglected
but indirect unitarity violation makes no difference, and demonstrate that the
experimental sensitivities to the neutrino mass ordering and a precision
measurement of \theta_{12} and \Delta_{21} \equiv m^2_2 - m^2_1 are robust.Comment: 21 pages, 6 figures, version to be published in PLB, more discussions
adde
Robust Spin Squeezing Preservation in Photonic Crystal Cavities
We show that the robust spin squeezing preservation can be achieved by
utilizing detuning modification for an ensemble of N separate two-level atoms
embedded in photonic crystal cavities (PCC). In particular, we explore the
different dynamical behaviors of spin squeezing between isotropic and
anisotropic PCC cases when the atomic frequency is inside the band gap. In both
cases, it is shown that the robust preservation of spin squeezing is completely
determined by the formation of bound states. Intriguingly, we find that unlike
the isotropic case where steady-state spin squeezing varies smoothly when the
atomic frequency moves from the inside to the outside band edge, a sudden
transition occurs for the anisotropic case. The present results may be of
direct importance for, e.g., quantum metrology in open quantum systems.Comment: 6 pages, 4 figures, accepted by Laser Physics Letter
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