5 ms·

I'm no cosmologist, but hasn't the effort to build detectors for these "heavy neutrino's" failed thus far? How much low hanging fruit is actually left? https:

• raattgift 9y ago
  It took twenty-five years to go from the solidification of the theory of a neutrino to account for missing momentum in beta decays to direct detection of the neutrino, and along the way atomic reactors and nuclear bombs were engaged in the effort. The problem is that detection relies upon the details of the recoil of atomic nuclei, and the recoil is much smaller for cold neutrinos than relativistic neutrinos, so we have detected pretty much exactly zero Cosmic Neutrino Background neutrinos directly, although there is plenty of indirect evidence from astrophysical observation. The interaction cross section of a "heavy neutrino"-like particle might be smaller than that of a neutrino of the same temperature (it might not feel the weak force at all, so caeteris paribus it might be many orders of magnitude less detectable just because the common interaction is purely gravitational), so not only is such a Cold Dark Matter candidate harder to detect (because cold ~ low recoil) but the interaction cross-section might be even smaller than that between the neutrino and a big atomic nucleus. > how much low hanging fruit is actually left There's no real way to answer that rigorously, as it really depends on what one means by "low hanging". Above neutrino floor? Below detector volumes in low numbers of cubic metres? Somewhere within the reach of existing technology at budgets less than the LHC? Somewhere within the reach of technology likely available in twenty years at budgets (adjusted for inflation and economic conditions) less than Super-Kamiokande?
  • noetic_techy 9y ago
    Interesting commentary. Are you a cosmologist? > although there is plenty of indirect evidence from astrophysical observation I'd be curious to see this if you have any links. > it really depends on what one means by "low hanging". Above neutrino floor? After reviewing this and neutrino masses, I see your point. Its hard to say.
    • raattgift 9y ago
      > if you have any links D'Amico et al.'s course notes, section 2: https://arxiv.org/abs/0907.1912 https://arxiv.org/abs/0907.1912 And from TASI (Theoretical Advanced Study Institute in Elementary Particle Physics) 2016, section III: https://arxiv.org/abs/1710.05137 https://arxiv.org/abs/1710.05137
    • raattgift 9y ago
      Ah, sorry, wires crossed in my head. I think you were asking for information about cosmic neutrino background detectability versus astrophysical/indirect evidence, right? On the latter: https://arxiv.org/abs/1412.5948 https://arxiv.org/abs/1412.5948 On direct detection: KATRIN collaboration: https://arxiv.org/abs/1602.03347 https://arxiv.org/abs/1602.03347 KATRIN is pretty cool. Pretty pictures of some of the apparatus: http://www.dw.com/en/the-katrin-tritium-neutrino-experiment-a-giant-scale-for-the-tiniest-of-particles/a-36044018 http://www.dw.com/en/the-katrin-tritium-neutrino-experiment-... But KATRIN is to detect warm neutrinos from a known source. As noted in the collab's paper (preprint link above), detecting ambient cold neutrinos would require a different, and larger, apparatus. We may need something much bigger even than that for direct neutrino-like cold dark matter detection. :-( So that gives you a sense of physical scale of what "low hanging fruit" might entail. ETA: also wikipedia is reasonable on this point https://en.wikipedia.org/wiki/Cosmic_neutrino_background?oldformat=true#Indirect_evidence_for_the_C%CE%BDB https://en.wikipedia.org/wiki/Cosmic_neutrino_background?old...