

Opera detects its fifth tau neutrino - user_235711
http://home.web.cern.ch/about/updates/2015/06/opera-detects-its-fifth-tau-neutrino

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TallGuyShort
Anyone know if this is this similar to the oscillation that many people think
accounts for the surprising mass of the 125 Higg's reported at the LHC? I was
surprised to read this as though it was something unique to neutrinos when I
had heard that theory proposed before. (edit: mind you, I've only heard it as
a possible explanation for Higgs bosons, whereas this is significant proof for
neutrinos).

For anyone interested, I recently finished Don Lincoln's "The Quantum
Frontier: The Large Hadron Collider" and "The Large Hadron Collider" (they're
kind of a series, although they have a lot of overlap). It's an excellent
coverage of the theory and practice of particle physics, and although he
doesn't cover the OPERA experiment at all,

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cshimmin
Regarding the Higgs mass, there are two basic camps in particle physics. Some
believe the Higgs mass is just a constant of nature (just like the electron
mass, or the speed of light), and there's nothing "surprising" about it, it's
just what it is. Others believe that this mass is surprising because of
"naturalness" issues -- the idea that this mass should have been more closely
related to other fundamental constants, namely the Planck mass. However it is
possible to view this suspicion as an aesthetic issue of the underlying
mathematical framework (QFT). One of the main motivating features of
Supersymmetry is to reconcile this difference by providing a mechanism by
which the Higgs mass "naturally" becomes much less than the Planck mass.
However many SUSY theories have been tightly constrained by recent
experiments, requiring ever more contrived ways to cause this "natural"
cancellation for a Higgs at 125 GeV.

The oscillation of neutrinos is completely different. In the standard model of
particle physics, neutrinos are treated as identically massless. However,
experiments have shown that one flavor of neutrino can spontaneously transmute
into another flavor. This phenomenon is (as far as we know) only possible if
the neutrino has some (albeit tiny) mass. This has been observed extensively
by other experiments that showed electron/muon neutrino oscillation, but OPERA
is providing a direct measurement of muon->tau neutrino mixing.

~~~
jabits
Excellent! Thanks.

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ars
How can they tell it's from the beam and not from say, the Sun? Or other
random galactic neutrinos?

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cperciva
I'm guessing the sun is easily ruled out based on the direction the neutrino
was travelling (as measured by the momentum of the particle produced when the
neutrino interacts with something).

"Random galactic neutrinos" are probably a statistical exclusion: Although
there _could_ be a tau neutrino coming from the same direction as the
experimental neutrino source, there aren't enough of them to create any
significant chance of the observation being anything other than an
experimental neutrino.

