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posted by martyb on Wednesday November 28 2018, @04:15AM   Printer-friendly
from the What-happened-to-oldtrinos? dept.

FTFA:

Neutrinos have always been good for surprises. The postulate of their existence by Wolfgang Pauli in 1930 was already revolutionary. Later, physicists learned that neutrinos oscillate, meaning that the three known neutrino “flavors” (electron, muon, and tau) periodically convert into one another as they travel through space—a neutrino born in the muon flavor, for instance, may later be detected as an electron neutrino or tau neutrino. The discovery of neutrino oscillations implied that neutrinos have nonzero mass, which required a modification of the standard model of particle physics. Adding another surprise, the parameters that govern neutrino oscillations turned out to be vastly different from theoretical expectations.

Now, the MiniBooNE experiment at Fermilab in Illinois has reignited excitement about neutrinos on yet another front. Data from the experiment suggest that muon neutrinos convert into electron neutrinos over distances that are too short for conventional neutrino oscillations to occur. This finding is all the more intriguing when considering that an earlier experiment—the Liquid Scintillator Neutrino Detector (LSND) at Los Alamos—already observed a similar signal in the late 1990s. The reason for excitement is that these signals could be beacons of sterile neutrinos, particles that only interact through gravity and aren’t foreseen in the standard model. The existence of sterile neutrinos could lead us to answers to some of the most pressing puzzles in physics—from the nature of dark matter to matter asymmetry in the Universe.

Journal article here

Note that most other physicists in the neutrino community think that the MiniBooNE folks have done their systematic error analysis wrong, in particular that the pi0 background shown in Fig. 1 of the paper is underestimated.


Original Submission

 
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  • (Score: 5, Interesting) by MichaelDavidCrawford on Wednesday November 28 2018, @08:06AM

    by MichaelDavidCrawford (2339) Subscriber Badge <mdcrawford@gmail.com> on Wednesday November 28 2018, @08:06AM (#767248) Homepage Journal

    The Solar atmosphere is opaque to light until that atmosphere is cool enough to permit electrons to bind to nuclei, primarily hydrogen but because our Sun is the child of a Supernova, there are lots of other varieties of nuclea too. The thin layer that's so cool enough is called the Photosphere, because that's what appears to us to be the surface of the Sun. At longer radii, the photons fly freely. (Photons interact with charged particles, so the ionized gas inside the photosphere is always scattering off the photons.)

    For the photons to complete the Random Walk from the Core to the Photosphere takes about 8,000 years.

    The first really effective Solar Neutrino detector found that the Sun was emitting one-third of the Neutrinos that was predicted by theory. Perhaps the Sun's Core ran out of fuel 8,000 or less years ago and we're just _now_ getting the bad news!

    Let's hope there's some _other_ explanation that's not yet predicted by the Standard Model; it happened that that particular detector was sensitive only to Electron Neutrinos. For Neutrinos to oscillate between Muon and Tau would explain the discrepancy, however it took some time to detect the oscillation. When I was at CERN in '93 somehow pointed out to me a tall, wide mound of dirt then explained that dirt was shielding a whole bunch of photographic film. You can make a pure Neutrino beam by shooting a beam of just about any particle into a long, dense barrier, for example a whole bunch of concrete or iron. (Iron is the most stable element.)

    --
    Yes I Have No Bananas. [gofundme.com]
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