8,847 research outputs found
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
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Search for the dipole portal of heavy neutral leptons at future colliders
In this paper, we study the potential of future colliders to explore the
parameter space of heavy neutral leptons (HNLs) through the dipole portal. We
consider hadron colliders such as the LHC in the high luminosity phase and
FCC-hh, and lepton colliders, such as FCC-ee. We consider various signatures
for the HNLs, including the missing energy signature and displaced decays, and
discuss the complementarity between the hadron and lepton colliders. In
particular, we find that thanks to a much clearer environment, FCC-ee may
search for the HNLs with masses up to and proper
lifetimes , which is well beyond the reach of the
experiments to be launched in the next decade.Comment: 13 pages, 10 figure
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