The Standard Model of our world, which most physicists accept, is incompatible with well-documented neutrino discoveries.
Sabine Hossenfelder, a theoretical physicist, examines a rising actual enigma in physics involving the “outsider” particle, the neutrino.
The neutrino, according to Fermi National Accelerator Lab, is:
It’s one of the so-called basic particles, which implies it’s made up of no smaller components that we’re aware of. Neutrinos belong to the same family as the electron, the most well-known basic particle (which powers the gadget you’re reading this on). Neutrinos, on the other hand, have no charge at all, while electrons have a negative charge.
Neutrinos are likewise very light and tiny. They have a little amount of mass. They are the lightest of all the mass-bearing subatomic particles. They’re also quite common—in fact, they’re the universe’s most prevalent large particle. Neutrinos occur from a variety of places and are often the result of heavy particles decaying into lighter ones, a process known as “decay.”
Despite this, Hossenfelder claims that neutrinos are “decidedly weird”:
To begin with, they are the only particles that interact with the weak nuclear force alone. The electromagnetic force, the strong nuclear force, or both interact with all other particles we know. And the nuclear force is ineffective. That’s why neutrinos hardly never interact with anything. Most of the time, they just travel through matter without leaving any trace. This is why they’re frequently referred to as “ghostly.” Approximately twelve to fifteen neutrinos have traveled through you while you were listening to this text.
This isn’t the only strange thing about neutrinos. What’s more bizarre is that the three different neutrino flavors mingle together. If you start with simply electron-neutrinos, for example, they will transform to muon-neutrinos as they travel. After then, they’ll revert to electron neutrinos. As a result, depending on how far you measure from a source, you’ll receive more electron neutrinos or muon neutrinos. Crazy! However, this is correct.
But there’s an odd aspect about it. Neutrinos would require mass to mix, but we don’t know how they gain mass, according to Hossenfelder. The Higgs boson, which links a left-handed form of the particle with a right-handed counterpart, gives mass to other basic particles. However, it seems that all neutrinos are left-handed.
But that isn’t the strangest thing. The strangest aspect is what occurred when physicists attempted to perform a long experiment in order to put all the data into a cohesive picture:
By 2005, researchers had got all the parameters correct except for one experiment which “did not make sense”: the Liquid Scintillator Neutrino Detector (1993–1998). Couldn’t it just be discounted? The trouble was, as Hossenfelder points out, “In particle physics, the discovery threshold is 5 sigma. The 3.8 sigma of the LSND anomaly wasn’t enough to get excited, but too much to just ignore.”
Well then the physicists tried again, starting in 2003 with a long running experiment with neutrinos at Fermilab called the MiniBooNE experiment (the Mini Booster Neutrino Experiment). It’s been running ever since because neutrinos interact only rarely.
Did all the new data erase the rogue findings?
Not at all. In 2018 MiniBooNE, which had accumulated more data, confirmed the findings from LSND. “Yes, you heard that right,” Hossenfelder reports. “They confirmed it with 4.7 σ, and the combined significance is 6 σ.” Not just 5 σ but 6.
These observations are not compatible with the Standard Model of our universe that most physicists accept. But there it is, and Hossenfelder does not think that the problem will be resolved any time soon.
Which goes to show that even a rigorous science like particle physics is not cut and dried; it can feature head-scratching anomalies. But then, if things weren’t like that, there might not be so many new facts and principles to discover. Or so many topics for science fiction.