A Major Physics Experiment Just Detected A Particle That Shouldn’t Exist

Scientists have produced the firmest evidence yet of so-called sterile neutrinos, mysterious particles that pass through matter without interacting with it at all.

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These scienticians really ought to stop playing with unknown particles. They’ve already flung us into a parallel universe where 2016 killed off several well-loved entertainers and made Trump POTUS.

Divine Angel said:

These scienticians really ought to stop playing with unknown particles. They’ve already flung us into a parallel universe where 2016 killed off several well-loved entertainers and made Trump POTUS.

And they thought Earth eating black holes were bad

Tau.Neutrino said:

A Major Physics Experiment Just Detected A Particle That Shouldn’t Exist

Scientists have produced the firmest evidence yet of so-called sterile neutrinos, mysterious particles that pass through matter without interacting with it at all.

more…

What!

There have been a dozen or so experiments already searching for the sterile neutrino and all of them drew a blank. I had concluded that they had been completely ruled out by experiment.

For a bit of background, I became aware of the possibility of sterile neutrinos back in the year … what’s 24 years ago? … late 1993.
It was then touted as an alternative explanation of dark matter.
But it would have easily observable consequences, it would mean that instead of the three levels of particles electron, muon, tau, there was a fourth, and that would affect measured masses of particles. Even back in 1993, the neutralino looked like a much more likely candidate for dark matter, but that has since been ruled out.

Let’s see what wiki says.

Ah wait, it interprets sterile neutrinos differently. Instead of a single fourth layer on top of electron, muon, tau it says that there are hypothesised to be three sterile neutrinos that are the right-handed counterparts of the normal left-handed neutrinos. “The existence of right-handed neutrinos is theoretically well-motivated, as all other known fermions have been observed with left and right chirality, and they can explain the observed active neutrino masses in a natural way. The mass of the right-handed neutrinos themselves is unknown and could have any value.”

“Sterile neutrinos allow the introduction of a Dirac mass term as usual. This can yield the observed neutrino mass, but it requires that the strength of the Yukawa coupling be much weaker for the electron neutrino than the electron, without explanation. Similar problems are observed in the quark sector, where the top and bottom masses differ by a factor of 40. Unlike for the left-handed neutrino, a Majorana mass term can be added for a sterile neutrino without violating local symmetries. However, this would still violate total lepton number.”

I’ve been keeping an eye out for majorana sterile neutrinos – plenty of searches with nothing found so far.

Nothing on the sterile neutrino yet except for hints that have been eliminated by more accurate experiments. One hint prior to 2006 at the Liquid Scintillator Neutron Detector (LSND) was refuted in 2006 (Cosmology) and again in 2007 (MiniBooNE). A second hint in 2016 from Daya Bay is also incompatible with the cosmology results from 2006. This new third hint in 2018 comes from MiniBooNE, the same machine that in 2007 eliminated the LSND find.

Some people complain about my using 3 sigma as a guide to acceptable probability.

The MiniBooNE results claim a 4.8 sigma result for detection of the sterile neutrino. When combined with LSND results they claim that increases to 6.1 sigma.

So they’ve solved the number one mystery of our age: “What is dark matter made from?”

Or have they?

Technical paper at https://arxiv.org/pdf/1805.12028.pdf

So, let’s look at what cosmology says.

From a 2013 paper:

“It was shown that, under the CMB+BAO constraint, when taking the sterile neutrino into account, the inconsistencies with Planck are improved from 2.4σ to 1.0σ for Hubble constant observation, from 4.3σ to 2.0σ for Sunyaev-Zeldovich (SZ) cluster counts observation, and from 2.3σ to 1.7σ for cosmic shear observation. A natural choice is to consider the model with light sterile neutrinos.”

How light?

The mass of the sterile neutrino from cosmological results has to be less than 0.73 eV. Or according to wikipedia, 99.9% confidence less than 0.44eV.

The mass of the sterile neutrino from the Daya Bay experiments was 5 MeV. So that’s ruled out.

The mass of the sterile neutrino from the new MiniBooNE experiments is 200 to 1250 MeV. So that’s also ruled out.

What did the MiniBooNE group do wrong? Well for starters, they only looked at two-neutrino oscillations, which is what caused the original LSND results to come to grief.

According to my amateur understanding, anyway.

I’d say the jury is still out on this one. Until independent confirmation arrives.