Would sterile neutrinos as an oscillation really change anything about dark matter? The total mass of neutrinos doesn't change, just the lepton number.
Much more interesting (and not touched on by the article as far as I noticed): The electron neutrino is the "partner" to the electron. The muon neutrino is the partner to the muon, and the tau neutrino to the tau. What's the sterile neutrino the partner to? (Or doesn't it have one, and that's what makes it "sterile"?)
If there is a partner to it, does the partner have mass? Does it interact in any way besides gravitationally? If not...
So either they aren't produced by beta decay, or they are but they can't be captured by gallium, or we're seeing a sterile neutrino in a different sense. ("Sterile" because it can't interact with gallium, but not sterile due to chirality.)
If I understand, the conversion of gallium into germanium is exactly a beta interaction. (But I may not understand, because it seems to me that gallium->germanium should emit a neutrino, not absorb one.) So I have a hard time seeing how a neutrino could be emitted by the source, but not absorbed by gallium. I could more readily see it as saying that there's a fourth type of neutrino that they cycle through, and while in that fourth state it can't convert gallium. But that wouldn't be "sterile" in the chirality sense.
In a "standard" beta decay the neutron turns into a proton and emits an electron and an anti-electron neutrino. In this reaction its absorbing an electron neutrino and emitting an electron (while still turning the neutron into a proton). Absorbing an electron neutrino is pretty much equivalent to emitting an anti-electron neutrino.
Neutron-Neutrino interaction?
https://www.vivaxsolutions.com/physics/feynman-diagrams.aspx
I even seem to remember that the most commonly produced neutrinos are antineutrinos (so the anti aspect is more fundamental than a convention for each particle type).
Would it though? It's not like we know neutrino mass from measurement, rather we estimate it from nuclear reactions that have occurred. The estimate would not change if a neutrino oscillates into a sterile one.
It would be a very unusual partner that has no concerved quantum numbers, and only mass.
A sterile neutrino would also imply that the neutrino is a Majorana particle (because it would have not quantum numbers that could be "anti").
https://arxiv.org/abs/1303.6912
Just as I am disappointed that "global warming" changed into the more ambiguous "climate change", I'm a little disappointed that the "right-handed neutrino" has turned into the "sterile neutrino". It's really strange that we only observe left handed neutrinos and either the revelation that there is a hidden right-handed neutrino or that neutrinos are fully Majorana particles without a right-handed form would be absolutely groundbreaking.
My take on it is that the neutrino mass term is not "physics beyond the standard model" but rather a "missing part of the standard model" and that one way or another, neutrinos hold an important secret, if not the important secret of the universe. (Note potentially three generations of right-handed neutrinos could exist at three mass scales and explain the gallium anomaly, cold dark matter, and the rarity of antimatter)
(Also as a climatologist I have no idea what the handedness of neutrinos even means. Something with spin?)
Indeed, it's the relation of spin to linear momentum of the particle.
Imagine I have a particle which is spinning in the same direction as its linear momentum (so positive helicity) but then I speed myself up really fast so now I'm going faster than it. Its linear momentum (to me) appears to have switched sign but its spin hasn't so the helicity has flipped.
Chirality is a more complicated thing which avoids this "problem" with helicity. Chirality doesn't change when the observer changed velocity.