Neutrinos questioned

By Wolfgang G. Gasser


1999-10-06

By Jim Carr on neutrinos in "Question about Gamma rays":

One can create all sorts of strawmen, but the fact is that there is such a "new particle", a fact that has been known for over 40 years except to a small group of people living in a fantasy world. And, yes, there was both missing momentum and missing energy in the reactions that were studied -- all of which was found once the experiments reached the necessary sensitivity.

'Constructing Quarks', 'A Sociological History of Particle Physics', Andrew Pickering, 1984, page 68:

"Beta decay, the emission of electrons and positrons from unstable nuclei, was one of the principal themes of radioactivity research in the early decades of the twentieth century. It was an especially puzzling phenomenon that electrons were emitted over a range of energies; their energy spectrum was continuous, rather than discrete as expected for transitions occurring in a quantized system. Amongst the fathers of quantum mechanics, Bohr, Heisenberg and Pauli each proposed radical explanations for this observation - Bohr, that energy was not exactly conserved; Heisenberg, that space-time was not continuous - but it was Pauli's proposal that won the day."

Can somebody explain me why it was assumed that electrons emitted during beta decay should not have a continuous energy spectrum?

Can somebody explain me why the continuous energy spectrum of electrons emitted during beta decay cannot be explained in a simple way but needs a "radical explanation"?

Two other extracts from the same book (p.6, p.395):

"First, scientists' understanding of any experiment is dependent upon theories of how the apparatus performs, and if these theories change then so will the data produced."

"They had been monitoring 140 tons of iron for 131 days and had observed around 200 events. Almost all of these could be ascribed to the passage through their apparatus of muons, generated by neutrino interactions in the overlying rock, but the experimenters concluded that three events could not be so explained."

The experiment of the 'existence' of neutrinos should be repeatable. Before one carries out the experiment, it should be possible to calculate the result (but there are so many types of neutrinos with the possibility of changing into other types, that I am not sure). The confirmation of this result by the experiment is considered a scientific conclusion of the existence of neutrinos.

But at least in such and similar cases, the conclusions depend much more on a theoretical framework and even on ad-hoc-hypotheses than on the experimental data.

Experiments on the one hand and interpretation of the experimental data based on the neutrino hypothesis on the other had evolved parallel until finally (i.e. decades later) a repeatable experiment could be interpreted as a proof of neutrinos.

So the later discovery of this particle seems to me rather a consequence that Pauli once had "won the day" than a consequence of its existence.


1999-10-19

By Wolfgang:

" It was an especially puzzling phenomenon that electrons were emitted over a range of energies; their energy spectrum was continuous, rather than discrete as expected for transitions occurring in a quantized system. "

By Bryan W. Reed:

What does having a quantized system have to do with it?

www.sciam.com/askexpert/astronomy/astronomy16.html:

"The neutrino was originally proposed as a solution to a serious problem observed in the radioactive decays of certain atoms. In a process known as nuclear beta decay, one of the neutrons in the decaying nucleus is transformed into a proton, accompanied by the emission of an electron. The law of conservation of energy -- one of the most basic principles of physics indicates that all the electrons produced in this way should carry the same energy, determined solely by the mass difference between the neutron and the proton (that mass would be converted into its energy equivalent)."

This reasoning makes sense only if one conceives atomic nuclei as quantized systems. If physicists had known what they know today, then probably nobody would have taken seriously the neutrino hypothesis for the continuous energy spectrum of the emitted electrons. According to sound reasoning it is expected that an electron emerging somewhere in the nucleus cannot leave the nucleus without any interactions at all. It seems logical that a neutron-decay at the edge of the nucleus can result in the maximal electron energy if the electron is emitted away from the nucleus. Pauli's original assumption that neither the position nor the emission direction of the emerging electron do matter, is not very reasonable.

By Wolfgang:

Can somebody explain me why it was assumed that electrons emitted during beta decay should not have a continuous energy spectrum?

By Bryan W. Reed:

It's a simple result of conserving energy and momentum.

It's not that simple because also [interaction with other nucleons and] gamma radiation is involved, and only in theory one can easily measure energy and momentum of all decay products of a single beta-decay.

By Wolfgang:

"First, scientists' understanding of any experiment is dependent upon theories of how the apparatus performs, and if these theories change then so will the data produced."

By Bryan W. Reed:

Yes and no.  Clearly the understanding of what's going on in an experiment is a function of what models you're using.  But the theory doesn't change the outcome of a given experimental measurement!

The author is confusing "data" and "interpretation."  Either that or the word "experiment" is being used ambiguously.

There are almost no data in theoretical physics without some form of interpretation. Most elementary particles are inferred from very complicated statistical interpretations of photomultiplier data. Photomultipliers do not work perfectly but register only a fraction of the incoming photons. So, not even the number of the 'actually' incoming photons is independent of the theory of photomultipliers. And the way from concrete numbers of photons to the conclusion of existence or inexistence of a particle such as a neutrino is normally long and often obscure.

If neutrinos do not emerge in beta decay, then also the occurrence of the inverse beta-decay reaction is no evidence of neutrinos, because conditions other than the assumed participation of neutrinos must be relevant.

The fact that the Nobel Prize for the 'experimental confirmation' of Neutrinos of 1956 was awarded only in 1995 could be further evidence that the experiment itself has not unambiguously suggested the existence of neutrinos.

I don't exclude the possibility that neutrinos exist, but until now I haven't seen anything really convincing. On the contrary, the many problems (e.g. deficit of solar neutrinos) could suggest that the whole neutrino concept is fundamentally flawed.


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