Weird neutrino excess won’t go away, hints at new physics

Enlarge / The interior of the MiniBooNE detector. (credit: Los Alamos National Lab)

There are several indications that our current understanding of the particles and forces that govern normal matter is wrong. Many of these areas seem to involve neutrinos, and that's in part because these particles rarely interact with normal matter, making them incredibly difficult to detect.

But we've gradually gotten better at building detectors, which has allowed us to discover that neutrinos have mass (something unaccounted for in the Standard Model) and shift among different identities as they travel. But the process has also revealed some persistent oddities. One oddity is a long-standing excess in one type of neutrino, first described by researchers from Los Alamos back in the 1990s. The same thing was seen at Fermilab in the initial runs of an experiment called MiniBooNE, but neither of them gathered enough data to announce discovery.

Now Fermilab is back with its latest update, using two additional years of MiniBooNE data. The excess is still there, and it has edged even closer to the statistical standards for discovery. If you combine the Fermi and Los Alamos data, we're already there. It's looking more and more like another break in the Standard Model, and the possible explanations include an entirely new type of neutrino.

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