Beta Decay, why did they have to resort to Neutrinos?

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Discussion Overview

The discussion revolves around the historical context and reasoning behind the introduction of the neutrino to explain beta decay. Participants explore the inadequacies of earlier models, particularly the "pool of energy" hypothesis, and the implications for conservation laws in nuclear physics.

Discussion Character

  • Historical
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants note that by 1931, the nuclear physics community proposed the neutrino due to the inability to explain beta decay without it, particularly because beta decay exhibited a wide energy spectrum compared to alpha and gamma decays.
  • Others argue that conservation of energy and momentum was not satisfied by beta decay, leading to the hypothesis of an additional undetected particle to balance the equations.
  • Some participants question why it took nearly two decades for the physics community to recognize the inconsistencies in beta decay, suggesting a lack of thorough examination of earlier papers.
  • There is a discussion about the nature of neutrinos, with some asserting that they are detectable due to their interactions, while others propose that the energy and momentum of incoming neutrinos are unknown prior to collisions.
  • One participant mentions that the initial hypothesis of a pool of energy in the nucleus would predict variations in mass of daughter nuclei, which would have required extensive experimentation to discern.
  • Another participant references historical papers that suggest alternative explanations for the energy spectrum of emitted electrons, indicating that the "pool of energy" hypothesis may not have been the only prevailing theory.

Areas of Agreement / Disagreement

Participants express differing views on the historical understanding of beta decay and the role of neutrinos, with no consensus on the prevailing theories or the timeline of scientific acceptance. The discussion remains unresolved regarding the specific reasons for the abandonment of earlier hypotheses.

Contextual Notes

Participants highlight limitations in the historical understanding of beta decay, including the dependence on definitions and the complexity of energy and momentum conservation in the context of neutrinos. There are references to specific historical papers that may not be widely accessible or in English.

  • #31
malawi_glenn said:
It matched good enough in the 1930's at least to call Fermi's theory a "success".
Fermi's theory did not predict a phase-space like spectrum (see above), Indeed, one of the successes of the theory was that it got the spectrum right.
 
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  • #32
Vanadium 50 said:
But not 3-body phase space. You need the q^5/M_W^4 to match data,
Sure, but that was explained theoretically only later by Fermi's weak-interaction model, using Pauli's hypothesis about the particle we call neutrino today (in 1930 Pauli called it neutron, but then they named the neutron neutron, which was discovered in 1932; so finally the name neutrino was given to Pauli's hypothetical particle).
 
  • #33
GregM said:
@mfb @hutchphd @Vanadium 50 @vela
Thanks for your comments. I take it that you, like me, haven't found a list of papers from 1911~1929AD on hypotheses for beta decay energy sources.
I apologize for this delayed response. I came across this thread only just now, in the list of "suggested threads" at the end of a more recent discussion about beta decay.

While working on my PhD in experimental neutrino physics many years ago, I collected some photocopies of historical articles about the neutrino. The first item in that binder is a very nice historical summary with about 20 references to papers from the 1920s and 1930s:

Laurie M. Brown, "The idea of the neutrino", Physics Today, September 1978.

There's also this:

W. Pauli, "Zur älteren und neueren Geschichte des Neutrinos", based on a lecture he gave in 1957 and subsequently published in Aufsätze und Vorträge über Physik und Erkenntnisthorie (V. F. Weisskopf, ed., 1961). I found it in his Collected Scientific Papers (1964), vol. 2. This is also very readable (if you can read German, that is) and provides some more references to early papers.
 
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