London, June 23 (ANI): A ghostly particle, whose existence was dismissed some three years earlier, is showing signs of life raising hopes that it could help explain the excess of matter over antimatter in the universe.
Neutrinos are subatomic particles that rarely interact with ordinary matter.
They are known to exist in three types: electron, muon and tau.
Each of these is able to spontaneously transform into another.
In the 1990s, results from the Liquid Scintillator Neutrino Detector (LSND) at the Los Alamos National Laboratory in New Mexico suggested there might be a fourth type: a "sterile" neutrino that is even less inclined to interact with ordinary matter than the others.
However, in 2007 the Mini Booster Neutrino Experiment (MiniBooNE) at the Fermi National Accelerator Laboratory in Batavia, Illinois, failed to find evidence of them.
But looks like sterile neutrinos were dismissed too soon.
While MiniBooNE used neutrinos to find the sterile neutrino, LSND used antineutrinos - the antimatter equivalent.
Although antineutrinos should behave exactly the same as neutrinos, just to be safe, the MiniBooNE team decided to repeat the experiment - this time with antineutrinos.
Interestingly, the team saw muon antineutrinos turning into electron antineutrinos at a higher rate than expected - just like at LSND.
MiniBooNE member Richard Van de Water reported the result at a neutrino conference in Athens, Greece, on 14 June.
According to Fermilab physicist Dan Hooper, who is not part of MiniBooNE, the excess could be because muon antineutrinos turn into sterile neutrinos before becoming electron antineutrinos, reports The New Scientist.
He said: "This is very, very weird."
Although it could be a statistical fluke, Hooper suggests that both MiniBooNE results could be explained if antineutrinos can change into sterile neutrinos but neutrinos cannot - an unexpected difference in behaviour.
The finding would fit nicely with research from the Main Injector Neutrino Oscillation Search, or MINOS, also at Fermilab, which, the same day, announced subtle differences in the oscillation behaviour of neutrinos and antineutrinos.
Antimatter and matter are supposed to behave like mirror versions of each other, but flaws in this symmetry could help explain how our universe ended up with more matter. (ANI)