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

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

#41

Post by Iolaum »

hprotagonist wrote: post #20
ncmncm wrote: post #7

Earlier quoted context omitted.

But, as noted, that already happened . Six sigma is six sigma. To demand better than that amounts to special pleading. 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 physicis…

we have a confirmed discrepancy at six sigma, sure. wanna bet how long it'll take to figure out _how_, at such a low detection rate? We're at "we've confirmed there's a bug", not "here's the repro, traceback, and by the way if you fix these four lines it'll work again".

Coming up with potential "tracebacks" is how theoretical physicists make papers and get citations. And then you use them to design a proper experiment that will shed light to other aspects of this anomaly.

But for some reason this process ain't starting.

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

#42

Post by misnome »

rpz wrote: post #14

Why do we need a particle accelerator to run experiments on neutrinos, given their apparent abundance? Is there any other way to observe neutrinos without a particle accelerator?

Energy ranges, knowing exactly how far you are from the source of the neutrinos, and background exclusion.

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.

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

#43

Post by misnome »

frutiger wrote: post #39
icegreentea2 wrote: post #29

Earlier quoted context omitted.

If you want to measure neutrinos transforming, then knowing the distance to source lets to calculate rate of transformation.

Why can't you sample at one point on the earth's surface and sample again at that point's antipode? You would know the distance that was travelled, and have measurements at both points.

How would you know the two different neutrinos interactions came from the same source/distance without producing them yourself?

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

#44

Post by misnome »

_Microft wrote: post #40
ars wrote: post #38

Earlier quoted context omitted.

How do they know they are only detecting neutrinos from the designated source, and not also other neutrinos mixed in?

I am not an expert on this, so take it with a grain of salt: Neutrinos are not directly detected. What happens is that they interact with matter in a medium and produce muons or electrons that are moving faster than the speed of light in that medium. That's only possible because the speed of light in said medium is less than the speed of light in vaccuum by the way. These fast-moving, charged particles lead to the ge…

This is somewhat correct, but talking about only one class of experiment (Cherenkov detectors).

Indeed it’s the child-particles of the interactions that are observed, so, electrons muons and Tau particles. Depending how you are measuring, (many approaches) these interactions are generally separable - and usually you can get some directionality out of your measured event - so you know the direction it came from.

Combining the direction with timing - with an accelerator you know exactly when the pulse of neutrinos were produced - this means you can exclude a very large amount of background.

Some background does get through, but you can measure it with e.g. the source turned off as you suggest, or the times when you know the source isn’t otherwise producing (like in between pulses) to get a background rate. You then generate enough data from the source to effectively “drown out” the background.

Much the same can be done with reactor sources - very often when building an experiment with a reactor as a source, there will be some government-level agreement to allow knowledge of what power the reactor is being run at, as well as shutdowns.

Along with Cherenkov, there are and have been scintillator, chemical-energy-deposition, Photographic film and even ocean-audio based methods of detection. Probably some more exotic ones I am forgetting also.

(I did a PHD in neutrino physics, although been out of the field a few years)

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

#45

Post by _Microft »

misnome wrote: post #44
_Microft wrote: post #40

Earlier quoted context omitted.

I am not an expert on this, so take it with a grain of salt: Neutrinos are not directly detected. What happens is that they interact with matter in a medium and produce muons or electrons that are moving faster than the speed of light in that medium. That's only possible because the speed of light in said medium is less than the speed of light in vaccuum by the way. These fast-moving, charged particles lead to the ge…

This is somewhat correct, but talking about only one class of experiment (Cherenkov detectors). Indeed it’s the child-particles of the interactions that are observed, so, electrons muons and Tau particles. Depending how you are measuring, (many approaches) these interactions are generally separable - and usually you can get some directionality out of your measured event - so you know the direction it came from. Combi…

Thanks for the reply, it is very much appreciated!

I did not know that "ocean-audio based methods of detection" for neutrinos are even possible and will certainly look that up later.

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

#47

Post by hprotagonist »

Iolaum wrote: post #41
hprotagonist wrote: post #20

Earlier quoted context omitted.

we have a confirmed discrepancy at six sigma, sure. wanna bet how long it'll take to figure out _how_, at such a low detection rate? We're at "we've confirmed there's a bug", not "here's the repro, traceback, and by the way if you fix these four lines it'll work again".

Coming up with potential "tracebacks" is how theoretical physicists make papers and get citations. And then you use them to design a proper experiment that will shed light to other aspects of this anomaly. But for some reason this process ain't starting.

> But for some reason this process ain't starting.

or, 2.5 years, one of which was a global pandemic, is not enough time to design, begin, and publicize a series of experiments that take a few decades to produce data in quantity to continue investigating new physics.

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

#48

Post by candiodari »

misnome wrote: post #43
frutiger wrote: post #39

Earlier quoted context omitted.

Why can't you sample at one point on the earth's surface and sample again at that point's antipode? You would know the distance that was travelled, and have measurements at both points.

How would you know the two different neutrinos interactions came from the same source/distance without producing them yourself?

Well that's not the problem. The problem is natural sources are too big. The distance difference between you and the top of the sun and the middle is like 100x the length of the equator. Neutrino sources in the sun have very irregular shapes, so that too changes the distance. And you have zero control over it all. All you'd ever see is the equivalent of a soft shadow, you'd never get a point source.

The second thing you might want to do: "filter" neutrinos ... well that just doesn't work at all. Nothing stops (a decent amount of) neutrinos. So you can't filter them and create a known point with, say, only electron neutrinos like you can with light. There are also no known astronomical objects that filter neutrinos. They fly right through a star, so that's no good either.

Third you could filter observations. But again you hit the filter problem. You can focus neutrinos measurements (even if you can't focus the neutrinos themselves), but that lowers the amount of neutrinos you measure further. And you're only measuring like maybe 50 per cubic meter of water, so you don't have much to work with.

I guess you could wait for things to get especially good for your measurement but you'll be waiting a long time.

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

#49

Post by fuzzfactor »

tim333 wrote: post #15
fuzzfactor wrote: post #11

>Maybe people just don’t like neutrinos? My sentiment exactly.

There's a poem about that https://www.symmetrymagazine.org/article/february-2011/decon...

I appreciate that.

It was truly as uplifting as it could be.

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