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B Do electron antineutrinos interact with anything?

  1. Oct 10, 2017 #1
    Do electron antineutrinos interact with anything?
     
  2. jcsd
  3. Oct 10, 2017 #2

    mfb

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    Sure. They can lead to inverse beta decay (antineutrino+proton -> positron+neutron), they can do elastic scattering (transfer some of their energy to other particles, e. g. electrons or nuclei), and at high energies even more reactions are possible.
     
  4. Oct 10, 2017 #3

    Orodruin

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    Coincidentally, electron anti-neutrinos were the first neutrinos ever to be discovered by experiments.
     
  5. Oct 11, 2017 #4
    I remember reading about that when reading for an answer to my question (Wolfgang i think). It was through deduction that there "must be" another particle. Interesting side note from wiki says Niels Bohr was "ready to accept" that energy was not conserved!

    I appreciate that being experimentally confirmed means they interact with things, I should've have put the question as do they interact with things more frequently than the other neutrinos.


    It seemed strange to me that electron anti-neutrinos are the least massive of the neutrinos, have no charge and still can interact with stuff. Then read more about the left hand / right hand spin (compared to momentum) and remembered I was told here (I think it was Orodruin :) that spatial non-parity refers to this, in that b- decay results in pretty much left hand only electron anti neutrinos.

    So is that why these neutrinos can interact with stuff while the other neutrinos rarely do?

    Thanks mfb from what you said I went on to read about the experiment that detected them. So apparently when the electron anti neutrino interacts with a proton it eventually leads to positron and electron annihilation in turn making gamma rays!

    I just got a veil of tritium. I find it odd that this tiny thing is making positrons and gamma rays! Is it actually doing that? I'm trying to understand if this veil of tritium is radiating these electron anti neutrinos to some great distances or if they all stay inside the tiny veil.
     
  6. Oct 11, 2017 #5

    Orodruin

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    This is different from what I was talking about. I was talking about the experimental direct detection of neutrinos in 1956. Not the theoretical introduction of the neutrino by Pauli in 1930. Pauli a priori just thought about a single neutrino participating in beta decays, he had no idea about neutrino flavours. Neither did the experimentalists in 1956, but in effect what they were seeing were electron anti-neutrinos.

    None of the flavour eigenstates have definite masses. You cannot talk about a flavoured state being the "least massive".
     
  7. Oct 11, 2017 #6
    I hear ya, I was just saying they where looking for it. post experimental confirmation I like to give credit to the peep who deduced such a thing exists.

    Thanks for the correction about the mass, I likely confused the mass of the electron, muon, tau with the neutrino counterparts.

    From the bit of reading I've done particles seem so interesting, I better understand the love for particle accelerators...very cool.
     
  8. Oct 11, 2017 #7

    mfb

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    All neutrino types rarely interact with matter.
    It does not. The decay is neutron -> proton + electron + electron antineutrino. The antineutrinos escape to space (well, something like 99.99999999999999% of them, didn't count the "9"s).
     
  9. Oct 11, 2017 #8
    And all antineutrinos of tritium decay do escape. Because the detection reaction is electron antineutrino + proton -> neutron + positron. Which requires the antineutrino to meet a high energy threshold. And antineutrinos from tritium decay cannot.
    Low energy antineutrinos do interact with matter. But the only legal interaction they have is elastic scattering. If the antineutrino from your vial of tritium does undergo elastic scattering off a nucleus or an electron on its way up to space and is reflected back down (an event of very low probability), all that happens is that it passes through Earth and escapes to space in another direction. If it undergoes the second elastic scattering on its passage through Earth (massively unlikely again, though slighltly less unlikely than scattering on the way up through air), all that happens that it escapes to space in third direction.
     
  10. Oct 12, 2017 #9

    mfb

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    There are nuclei where this reaction doesn't have any threshold. They are naturally radioactive then. That typically doesn't make them suitable for neutrino detectors, but that was not the question.

    Inverse beta decay of tritium has been suggested as detector for the cosmological neutrino background (not antineutrinos): PTOLEMY.
     
  11. Oct 12, 2017 #10

    Orodruin

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    PTOLEMY was not first in suggesting this. As with many things, Weinberg is to blame.
     
  12. Oct 12, 2017 #11

    mfb

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    They didn't come up with the idea, but they came up with a detector proposal and they run feasibility studies and component tests (which qualify as their own experiments).
     
  13. Oct 12, 2017 #12
    Thanks mfb, that clarifies it for me. funny to catch myself starring at this tiny glowing veil in awe of its "mechanics"...well into the mechanical watch it goes lol
     
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