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The MiniBooNE experiment at Fermilab may have found hints of a new particle

bbc.com

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Re: The MiniBooNE experiment at Fermilab may have found hints of a new particle

#11

Post by danharaj »

bdonlan wrote: post #10
sanxiyn wrote: post #8

Earlier quoted context omitted.

By definition, neutrinos interact with weak force and sterile neutrinos don't.

What interactions are left then? Neutrinos don't interact with the electromagnetic or strong forces, and I don't think we can observe gravitational effects in an accelerator, so how are we detecting these sterile neutrinos?

Neutrinos oscillate between different flavors. If a sterile neutrino exists then we will see deviations in the distribution of detected neutrino flavors because they will oscillate differently.

Re: The MiniBooNE experiment at Fermilab may have found hints of a new particle

#13

Post by dphidt »

DoctorOetker wrote: post #7
dphidt wrote: post #6

Earlier quoted context omitted.

Hi, neutrino physicist here. There are indeed a handful of results that point to a more-or-less consistent picture with sterile neutrinos, including MiniBooNE (now updated with 2x more data), LSND, antineutrinos from nuclear reactors, and calibrations of solar neutrino experiments (GALLEX/GNO and SAGE). All very different experiments with different uncertainties, which makes it hard to explain away. Meanwhile, there…

Hi, I have a couple of questions: If I understand correctly, as far as we thought there seem to be 3 flavours of neutrino (electron, muon, tau neutrinos), and neutrinos carry (kinetic) energy (and possibly some rest mass). Historically often "different" or "new" particles just turned out to be the same particle with different energy: Cathode rays and electrons are the same thing, but nobody would describe the electro…

The other comments are spot-on. I'll just add that the neutrinos flavors are defined by the way they interact: electron neutrinos interact to produce electrons, never muons. So they're quite different in that sense, and in the current Standard Model of particle physics, they're treated as independent particles. (This is not to say that in the future, we won't require a more comprehensive model that could relate particles in a deeper way.)

We know from experiments like LEP (electron-positron collisions) that there are only three kinds of neutrinos that participate in weak interactions (electron, muon, and tau). Thus the fourth neutrino type suggested by these anomalous oscillation measurements cannot interact via the weak force, meaning it doesn't interact at all,* hence sterile. The only way to detect them is through their influence on the oscillations of other neutrino types.

* They'd still feel gravity, which isn't included in the Standard Model anyway.

Re: The MiniBooNE experiment at Fermilab may have found hints of a new particle

#14

Post by dphidt »

sanxiyn wrote: post #9
dphidt wrote: post #6

Earlier quoted context omitted.

Hi, neutrino physicist here. There are indeed a handful of results that point to a more-or-less consistent picture with sterile neutrinos, including MiniBooNE (now updated with 2x more data), LSND, antineutrinos from nuclear reactors, and calibrations of solar neutrino experiments (GALLEX/GNO and SAGE). All very different experiments with different uncertainties, which makes it hard to explain away. Meanwhile, there…

On reactor antineutrino anomaly, what do you think of https://arxiv.org/abs/1806.00574 ? It seems to me both Daya Bay collaboration and RENO collaboration suggest anomaly is explained by nuclear fuel evolution.

It's really interesting work! Just a year or so ago, the features in the energy spectrum appeared to be independent of burn-up, so it's exciting to see higher precision data coming in. No matter what, we'll get a much better model for reactor antineutrino spectra.

It's about a year old, but I like this talk from Patrick Huber (one of the developers of the new reactor models), in particular his "Score Card" for the various evidence on slide 25: https://absuploads.aps.org/presentation.cfm?pid=13003. I keep this in mind as I am updating my personal priors :).

Re: The MiniBooNE experiment at Fermilab may have found hints of a new particle

#15

Post by ianai »

dphidt wrote: post #13
DoctorOetker wrote: post #7

Earlier quoted context omitted.

Hi, I have a couple of questions: If I understand correctly, as far as we thought there seem to be 3 flavours of neutrino (electron, muon, tau neutrinos), and neutrinos carry (kinetic) energy (and possibly some rest mass). Historically often "different" or "new" particles just turned out to be the same particle with different energy: Cathode rays and electrons are the same thing, but nobody would describe the electro…

The other comments are spot-on. I'll just add that the neutrinos flavors are defined by the way they interact: electron neutrinos interact to produce electrons, never muons. So they're quite different in that sense, and in the current Standard Model of particle physics, they're treated as independent particles. (This is not to say that in the future, we won't require a more comprehensive model that could relate parti…

Thank you so much for replying! I learned quite a bit.

What is the source of neutrinos in the experiments suggesting sterile nutrinos? Is it different from the non confirmations?

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