The physics anomaly no one talks about: What’s up with those neutrinos?

If you are too far from the source, the mixing you might be measuring might have happened already happened. You can build a detector right next to the source, and also far away, and correlate the differences.

External interference can be excluded on energy range, direction, and “timing” - you know exactly when the pulse happened in the source and can exclude things outside that window (as the neutrinos all travel at the speed of light to within measurement error).

Things like neutrinos from the sun can and have been measured, but for many things you want to measure you need more careful control.

That's part of the problem. Which Neutrinos are you measuring? The ones from your experiment, the ones from the Sun, the ones from the environment? They're exceptionally light particles, so effective shielding is difficult.

It's why a lot of these experiments are deep underground. The one I visited was in northern Minnesota in an old abandoned Mine placed half a mile under the surface and positioned in such a way to receive a neutrino beam all the way from Fermilab in Chicago.

The smaller and lighter the phenomenon, the larger your laboratory needs to be come.

https://en.wikipedia.org/wiki/MINOS

If there are sterile neutrinos... they are a possible dark matter particle.

> we have three flavors of neutrinos and these mix into each other as they travel….There are natural sources like the sun, and neutrinos that are created in the upper atmosphere when cosmic rays hit. And then there are neutrinos from manmade sources, particle accelerators and nuclear power plants. In all of these cases, you know how many neutrinos are created of which type at what energy. And then after some distance you measure them and see what you get.

1) As _Microft says in a sibling reply, the reason is because for this type of experiment, the researchers were studying short-baseline oscillations. A curious property of neutrinos is that they oscillate -- we interact with them through their "flavor", but they propagate through space in a mixture of flavor eigenstates, so a neutrino that is created as an electron-type neutrino can interact later as a muon-type (or tau-type) neutrino.

LSND and MiniBooNE study short-baseline oscillations, where L/E (the distance travelled divided by the particle energy) is very small, a few meters on a ~1MeV neutrino. By comparison, almost all the (vast number!) neutrinos that pass through each of us each second come from much farther away. Most of them come from the Sun, so their origin is distributed over a sphere 100x the diameter of the Earth (and, to make matters worse, something called the MSW-effect scrambles things further). So, people who study these effects either build an accelerator or snuggle up next to a reactor.

In principle, one could use the existing neutrinos from the Sun to do this sort of experiment, but one would need a material capable of blocking all of, say, the electron-type neutrinos from the Sun. If such a thing existed, we could place a detector a few meters away from that filter and watch for electron-type neutrinos to reappear. Alas, the only known material perhaps capable of achieving such a task exists for a fraction of a second inside core-collapse supernovae -- the extremely dense infalling matter is so dense that it can actually trap some of the outgoing neutrinos.... until the neutrino pressure blows it apart.

2) In this specific case, the experiments were originally done with muon anti-neutrinos. The easiest way to get those is with a particle accelerator.

3) One can also attempt to get at this sort of thing (though the approach has different sensitivity/systematics) through reactor-neutrino experiments, as one of the downvoted posts below suggests. For the shortest baselines, though, there's probably really nothing like a beam-experiment.

4) (an aside) One thing that Hossenfelder doesn't really address in the article: There are still systematic-uncertainty questions around LSND and Mini/MicroBooNE. The modern experiment has addressed many of them, but not all. The experiments are difficult and the anomalies have their quirks. Yes, the combined result reaches a statistical power of ~6-sigma, but I don't think you'll have to look too far to find credible experimentalists who have concerns about the result.

This is in contrast to something like the Higgs, where the discovery was fairly clean and simultaneously confirmed by two groups. LSND was huge news back in the day, but the difficulty/expense of replication and the substantial experimental challenges mean that the situation remains fairly murky.

Secondly, she mentions LSND which was a big tub of liquid that would interact with neutrinos that passed through it. Flashes from those interactions would be picked up by photo detectors (hence “scintillation”). The most famous such setup in a mine in Japan, but there are several such “neutrino telescopes”.

Particles without mass are required to travel at the speed of light. Particles traveling at the speed of light don't experience time in their own frame of reference. For instance a photon is emitted and absorbed at the same instance from its point of view. So they have no time to do anything like change properties.

It looks like people just wish this would go away, like the failure of the galactic rotation curves. What is strange is that this might be a place to park dark matter, catnip nowadays.

Usually when this sort of thing happens in cosmology, astrophysics, or particle physics, it is because most physicists hate working with the mathematics required, and hope somebody else will tell them they were right to ignore it.

They don't do anything, there is no use for them really, they don't even have many properties...

The only real effect they have is making physicists' maths a little more complex (or slightly wrong if they forget them).

I don't have the background to interpret these figures, and based on a quick search for MiniBooNE mentions in the paper, the authors don't seem to say that MiniBooNE is an outlier relative to all the other experiments. Where does the paper talk about the tension?

EDIT: based on the comments below, it sounds like the tension is between appearance-based and disappearance-based experiments, and isn't necessarily about a single experiment being an outlier relative to others?