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posted by janrinok on Monday June 04 2018, @08:54PM   Printer-friendly
from the sneaky-neutrinos dept.

From LiveScience.com: A Major Physics Experiment Just Detected A Particle That Shouldn't Exist

Physics just can't seem to stop churning out experiments with odd results. Will this one be the ONE that finally upsets the Standard Model?

Scientists have produced the firmest evidence yet of so-called sterile neutrinos, mysterious particles that pass through matter without interacting with it at all.

The first hints these elusive particles turned up decades ago. But after years of dedicated searches, scientists have been unable to find any other evidence for them, with many experiments contradicting those old results. These new results now leave scientists with two robust experiments that seem to demonstrate the existence of sterile neutrinos, even as other experiments continue to suggest sterile neutrinos don't exist at all.

That means there's something strange happening in the universe that is making humanity's most cutting-edge physics experiments contradict one another.

And from https://www.theregister.co.uk/2018/06/04/miniboone_sterile_neturinos/ we get:

The MiniBooNE experiment is straightforward: proton collisions (12.84 x 1020 protons, to be precise) emit neutrinos, and the instrument fired muon neutrinos at an oil tank. Some of those oscillated into electron neutrinos, so their interaction with the oil produce flashes that instruments can detect.

The oscillation rate is predictable, so even a few hundred extra electron neutrinos are a result.

Physicist and blogger Sabine Hossenfender explained the significance in this Tweet thread, in which she noted:

"The new data from MiniBooNE confirms that this tension in the data is real. This data can (to my best knowledge) NOT be fitted with the standard framework. It requires either new particles (sterile neutrinos) or some kind of symmetry violation. She added: "Now it's time for theoretical physicists to come up with an explanation"."

The known neutrinos – electron, muon, and tau – all interact via the electroweak force as well as gravity, which makes them identifiable by scintillators.

The hints that a sterile flavour might exist arise because of neutrino oscillations – the little blighters like to flip between different flavours.


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  • (Score: 4, Interesting) by HiThere on Tuesday June 05 2018, @03:03AM (4 children)

    by HiThere (866) Subscriber Badge on Tuesday June 05 2018, @03:03AM (#688701) Journal

    If that's the same article I saw elsewhere they didn't find a new particle, they found an effect that could be explained if this new particle existed. Not quite the same thing.

    OTOH, I don't think there is any prediction as to how more directly detect the "sterile neutrino". Even the ordinary ones are pretty hard to spot. So they found an effect that could be predicted from known values if you assume that a sterile neutrino existed with thus and such characteristics. In a way you could say "history repeats", since that was how the electron neutrino was first "discovered". ... And I consider those scare quotes quite valid and appropriate. It was actually discovered much later and even then things are a bit strange, since they can only be indirectly detected. (Except in really rare events like, if I've got this correct, reverse beta decay.)

    OTOH, this does appear to be a crack in the standard model, whatever the actual explanation turns out to be. A sterile neutrino is probably the least surprising possible interpretation.

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  • (Score: 0) by Anonymous Coward on Tuesday June 05 2018, @10:39AM

    by Anonymous Coward on Tuesday June 05 2018, @10:39AM (#688797)

    A sterile neutrino is probably the least surprising possible interpretation.

    The least surprising explanation is that there is something mundane wrong with the null model they are rejecting:

    was actually the result of bad calculations.
    [...]
    might turn out to be the "systematics,"

    https://www.livescience.com/62721-sterile-neutrino-detected-fermilab.html [livescience.com]

    Here is what they have to do:

    1) Assume the sterile neutrino with such and such properties*does* explain these results.
    2) Derive a *precise* prediction for the results of another experiment from a model that includes the sterile neutrino with those properties
      - eg if we do such and such then there should be a particle detected at x +/- y energy levels; but hopefully they can figure out something cheaper.
    3) Do that experiment and compare to the prediction. If the prediction is wrong, then forget it.

  • (Score: 2) by PiMuNu on Tuesday June 05 2018, @01:18PM (2 children)

    by PiMuNu (3823) on Tuesday June 05 2018, @01:18PM (#688833)

    > If that's the same article I saw elsewhere they didn't find a new particle, they found an
    > effect that could be explained if this new particle existed. Not quite the same thing.

    Surely that is true of all particles? I mean a table is "an effect that could be explained if protons, neutrons and electrons exist". Electromagnetism is "an effect that could be explained if photons exist", etc.

    • (Score: 2) by HiThere on Tuesday June 05 2018, @05:33PM (1 child)

      by HiThere (866) Subscriber Badge on Tuesday June 05 2018, @05:33PM (#688940) Journal

      To an extent that's true, but generally there are multiple effects that are explained by the same particle. When there's only one observed effect, the particle's a lot less certain. This is why it originally took neutrinos so long to be accepted. They weren't really accepted until other effects were found that were explained by the same particle. Multiple lines of evidence are a LOT more convincing than single lines, as they really narrow the plausible explanations down a lot more.

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      • (Score: 2) by PiMuNu on Wednesday June 06 2018, @08:40AM

        by PiMuNu (3823) on Wednesday June 06 2018, @08:40AM (#689229)

        Good answer!