That's a contentious statement! We're not sure if they are or aren't.
replyMore accurately: we aren't sure if antineutrinos are the same or different from neutrinos!
well either way they're in opposite helicity states...
but yes, Majorana neutrinos nothwithanding, there are plenty of transported positrons detected by e.g. PAMELA and plenty of antimuons that go long distances.
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