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R. N. Mohapatra
that the anti-neutrino number (flux) emitted is calculated. Then scientists put
neutrino detectors at a short distance from the reactor to measure the antineutrino flux, and found a shortage of the anti-neutrinos compared to the
calculated fluxes. A plausible explanation for this is that some of the antineutrinos are oscillating to a muon anti-neutrino, which cannot be detected.
This is because it can only produce an anti-muon which is however much
heavier than an electron (200 times), so the reactor anti-neutrino does not have
enough energy to produce them. But the distance which tells the frequency of
oscillation leads to the conclusion that the neutrino to which the electron antineutrino is oscillating has to have a mass near an eV, like in the case of LSND.
So if this conclusion is firmly established, that will support the LSND results.
There has been a serious and dedicated experiment to check the LSND results
at Fermi National Laboratory, called Mini-BooNe, which has also provided
some supporting evidence for a sterile neutrino. We must however caution
that there are some other oscillation experiments which seem to go against
this conclusion [35].Thus the jury is still out on this possibility.
The dark neutrino possibility suggests that it could be one of the new
neutrinos from the mirror sector. Of the three new neutrinos in the dark
(mirror) sector, the LSND neutrino could be one, since it meets all the
requirements for a sterile neutrino. This possibility is however not completely
free of difficulties, because this would contribute to the total energy of the
universe at the time of Big Bang Nucleosynthesis and alter the successes of the
standard three neutrino BBN (see Chap. 18.1).
There are also arguments to suggest that the dark matter of the universe
may be a sterile neutrino but with a mass in the keV range [39]. The known
neutrinos cannot be dark matter since they are so light, and if they were,
they would move so fast at the epoch of galaxy formation that they would
wipe out all structure. So the minimum mass they should have is about a
few kilo electron volts. This class of dark matter even without self-interaction
can explain why the galaxy centers do not have cusps and also several other
problems with the cold dark matter picture.
The theoretical implications of the existence of the sterile neutrino are so
profound [1] that there are currently many experiments trying to confirm
or refute this possibility. The jury is however still out on their possible
existence [24].
R. N. Mohapatra
that the anti-neutrino number (flux) emitted is calculated. Then scientists put
neutrino detectors at a short distance from the reactor to measure the antineutrino flux, and found a shortage of the anti-neutrinos compared to the
calculated fluxes. A plausible explanation for this is that some of the antineutrinos are oscillating to a muon anti-neutrino, which cannot be detected.
This is because it can only produce an anti-muon which is however much
heavier than an electron (200 times), so the reactor anti-neutrino does not have
enough energy to produce them. But the distance which tells the frequency of
oscillation leads to the conclusion that the neutrino to which the electron antineutrino is oscillating has to have a mass near an eV, like in the case of LSND.
So if this conclusion is firmly established, that will support the LSND results.
There has been a serious and dedicated experiment to check the LSND results
at Fermi National Laboratory, called Mini-BooNe, which has also provided
some supporting evidence for a sterile neutrino. We must however caution
that there are some other oscillation experiments which seem to go against
this conclusion [35].Thus the jury is still out on this possibility.
The dark neutrino possibility suggests that it could be one of the new
neutrinos from the mirror sector. Of the three new neutrinos in the dark
(mirror) sector, the LSND neutrino could be one, since it meets all the
requirements for a sterile neutrino. This possibility is however not completely
free of difficulties, because this would contribute to the total energy of the
universe at the time of Big Bang Nucleosynthesis and alter the successes of the
standard three neutrino BBN (see Chap. 18.1).
There are also arguments to suggest that the dark matter of the universe
may be a sterile neutrino but with a mass in the keV range [39]. The known
neutrinos cannot be dark matter since they are so light, and if they were,
they would move so fast at the epoch of galaxy formation that they would
wipe out all structure. So the minimum mass they should have is about a
few kilo electron volts. This class of dark matter even without self-interaction
can explain why the galaxy centers do not have cusps and also several other
problems with the cold dark matter picture.
The theoretical implications of the existence of the sterile neutrino are so
profound [1] that there are currently many experiments trying to confirm
or refute this possibility. The jury is however still out on their possible
existence [24].