In the arcane world of particle physics, the quasi-magical conclusion from indirect evidence that neutrinos can transform themselves from one of the species’s categories, or flavors in the parlance of the trade,  to another is a big deal. It was predicted theoretically in 1957 to no great instant acclaim. It became more respectable when experts decided it was the only way to explain a “missing neutrino” problem in the flux from our own sun’s core. Either the sun’s core was failing, it was feared (ok, nobody believed that), or some of its neutrinos had merely put on a disguise before they reached detectors on Earth. Not only that, but to don such a masquerade, neutrinos would have to have mass, travel just slightly slower than the speed of light, and contribute a jot to the overall universal tensor of gravity (not sure if tensor is the right word there but it feels right).

Thus for those who like to keep up on arcane doings in important fundamental science, direct and controlled confirmation of the process is also big news. Not front page, but more than meriting general circulation. This with a few exceptions it did not get in the US. (French outlets, judging by the Google hits on posts in French, gave it substantial coverage).

The news is that at CERN, the same lab near Geneva that houses the Large Hadron Collider, a beam of protons has been for a long time slamming into graphite targets. Among other debris, muon neutrinos flee the scene in a narrow beam along the Alps foothills and onward south. Intercepting their calculated path is a detector under Gran Sasso Mountain in Italy. For years its detector, which hardly detects anything what with neutrinos being so stealthy, has noticed the occasional muon neutrino coming through. Now, it has seen a tau in the flock. Ergo presto: it must’ve oscillated during its millisecond-short transit. And now they know what exactly a muon neutrino oscillates into.

Reporter-detectors who triggered on this news:

• Los Angeles Times – Thomas H. Maugh II: Physicists unlock mystery of subatomic particle ; Maugh walks readers as clearly as possible through some of the basics. His angle – that this helps explain dark matter – is defensible but perhaps overdone. That is, a presumption of neutrino mass, propelled by  many highly suggestive  measurements of apparent oscillation,  already is embedded in expert discussions on the topic. But this clinches the deal, I guess.
• Reuters -Robert Evans: Missing piece found in particle puzzle ; His angle, aside from the physics itself, is that this shows (even better than already shown) that aspects of the the standard model of physics are definitely wrong – and thus the LHC should deliver fun results on more ways it’s wrong.
• Science News – Ron Cowen: Neutrino quick-change artist caught in the act ; Interesting, in light of the first two ambiguous, one-size-fits-all-particle-physics headlines in the above bullets, that Science News has a readership on which its editors feel comfortable to spring “neutrino” right at the top. Cowen may over-amp the novelty of the result by using an opening clause both metaphoric and literal:  “In a truly transformative event…”  That’s good, as the news is about a transformation. But conceptually, this evidence does not launch the transformation of standard physics. It does button it down (or maybe tack it down – a few more data bits could rivet it down). The story stresses that this confirms what was widely and strongly suspected – ergo not a breakthrough. Note a nifty quote about missing bills turning up in a pilferer’s pocket.
• AFP – Marlowe Hood: Physicists solve mystery of missing neutrinos;
• New Scientist: Anil Ananthaswamy ; First ‘chameleon particle’ spotted after changing type ;

Grist for the Mill: CERN Press Release ;

- Charlie Petit

Pic source ;

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