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Theoretical physicist Sabine Hossenfelder offers a look at a burgeoning mystery in physics that involves the “outside” particle, the neutrino.
According to Fermi National Accelerator Lab, the neutrino is:
one of the so-called fundamental particles, which means that it is not made up of smaller pieces, at least as far as we know. Neutrinos are members of the same group as the most famous fundamental particle, the electron (which powers the device you are reading this about right now). But while electrons have a negative charge, neutrinos have no charge at all.
Neutrinos are also incredibly small and light. They have some mass, but not much. They are the lightest of all subatomic particles that have mass. They are also extremely common – in fact, they are the most abundant massive particle in the universe. Neutrinos come from all sorts of different sources and are often the product of heavy particles decaying into lighter particles, a process called “decay”.
But Hossenfelder tells us, having said that, that neutrinos are “decidedly weird”:
First, they are the only particles that only interact with the weak nuclear force. All other particles known to us interact with either the electromagnetic force or the strong nuclear force or both. And the weak nuclear force is weak. This is why neutrinos rarely interact with anything. Most of the time, they just pass through matter without leaving a trace. This is why they are often referred to as “ghostly”. While you listened to this sentence, about 10 to 15 neutrinos passed through you.
That’s not the only reason neutrinos are weird. What’s even weirder is that all three types of neutrino flavors mix together. This means that if you start with, say, only electron neutrinos, they will convert to muon neutrinos as they travel. And then they will convert back into electron neutrinos. So, depending on the distance from a source at which you make a measurement, you will get more electron neutrinos or more muon neutrinos. Crazy! But it’s true.
Sabine Hossenfelder, “The physical anomaly no one talks about: what’s going on with these neutrinos?” at ReturnRe(Action) (September 18, 2021)
But there is a weirder part. Neutrinos would need mass to mix together but, says Hossenfelder, we don’t know how they get mass. Other elementary particles get their mass from the Higgs boson, which couples a left-handed version of the particle with a right-handed version. But all neutrinos seem to be left-handed.
But that’s still not the weirdest part. The weirdest part is what happened when physicists tried to run a long experiment to put all the data together to get a coherent picture:
By 2005, the researchers had corrected all the parameters, except for one experiment that “didn’t make sense”: the Liquid Scintillator Neutrino Detector (1993-1998). Couldn’t that just be reduced? The problem was, as Hossenfelder points out, “In particle physics, the threshold for discovery is 5 sigma. The 3.8 sigma of the LSND anomaly was not enough to get excited about, but too much to simply ignore.
Well, physicists tried again, starting in 2003 with a long experiment with neutrinos at Fermilab called the MiniBooNE experiment (the Mini Booster Neutrino Experiment). It has worked since because neutrinos rarely interact.
Has all new data erased malicious findings?
Not at all. In 2018, MiniBooNE, which had accumulated more data, confirmed the findings of the LSND. “Yes, you heard that right,” reports Hossenfelder. “They confirmed it with 4.7σ, and the combined significance is 6σ.” Not just 5 σ but 6.
These observations are not compatible with the standard model of our universe accepted by most physicists. But there it is, and Hossenfelder doesn’t think the problem will be solved anytime soon.
This shows that even a rigorous science like particle physics is not cut and dried; he may have head-scratching abnormalities. But then, if things weren’t like this, there might not be so many new facts and principles to discover. Or as many subjects for science fiction.
You can also read: Philosopher: We cannot prove that we are not living in a simulation. David Chalmers takes a step-by-step look at the issues in an excerpt from his new book Reality+ and excludes proving it to be false. The question is not as simple as that, of course. We don’t have to take something seriously because we can’t prove it isn’t true.
