What is the significance of the Cabibbo Angle Anomaly in particle physics?

[mitchell porter]

These days, most particle physics anomalies (meaning, observations suggesting beyond-standard-model physics) eventually disappear under closer scrutiny. This one caught my eye because it can be attributed to the neutrino sector, which we understand least and which therefore has the most room for new physics.

https://arxiv.org/abs/2009.03877
Modified lepton couplings and the Cabibbo-angle anomaly
Antonio Coutinho, Andreas Crivellin, Claudio Andrea Manzari
[Submitted on 8 Sep 2020]
Significant discrepancies between the different determinations of the Cabibbo angle have been observed. Here, we point out that this "Cabibbo-angle anomaly" can be explained by lepton flavour universality (LFU) violating New Physics (NP) in the neutrino sector. However, modified neutrino couplings to Standard Model gauge bosons also affect many other observables sensitive to LFU violation, which have to be taken into account in order to assess the viability of this explanation. Therefore, we perform a model-independent Bayesian global analysis and find that non-zero modifications of electron and muon neutrino couplings are preferred at more than 99.99%C.L. (corresponding to more than 4σ). Our results show that constructive effects in the muon sector are necessary, meaning simple models with right-handed neutrinos are discarded and more sophisticated NP models required.

 

[robwilson]

I probably shouldn't say this, as it's absurdly speculative and not supported in any published or arxiv-ed papers that I know of, but when I looked in detail at the Cabibbo angle a few years ago, it seemed to me that there was evidence of a quantum gravity effect, which led me to suspect the influence of the Moon. I wasn't able to produce any really convincing evidence, however.

 

[Vanadium 50]

it seemed to me

I wasn't able to produce any really convincing evidence

Which is the difference between science (evidence) and philosophy (it seems to me).

 

[robwilson]

Which is the difference between science (evidence) and philosophy (it seems to me).

Very likely, although in my experience philosophy is usually much more rigorous than this. And science is often less rigorous. I didn't say I had no evidence, just that it wasn't convincing enough. The evidence is still there, and I may be able to use it one day, if I can work out a few more details.

 

[robwilson]

This paper provides evidence that the Cabibbo angle varies in a way that we don't understand. The effect may be real or it may not. We need more evidence. What evidence should we look for? First off, we should control for as many external factors as possible. That includes the gravitational field, since the "new physics" this paper speculates about could in principle be a quantum gravity effect. The best way to control for the gravitational field is to conduct the experiment in exactly the same place at different times of day, month and year. We may not find anything by doing this, but on the other hand we might.