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Particle mystery: physicists confirm the muon is more magnetic than predicted

sciencemag.org

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Re: Particle mystery: physicists confirm the muon is more magnetic than predicted

#171

Post by treyh »

atty wrote: post #110
treyh wrote: post #92

Earlier quoted context omitted.

My understanding is that with the lagrangian approach then the free parameters are not all interacting with each other because they are part of different terms. This means a change to a free parameter doesn't necessarily break experiments.

The point is that there are now 10s-100s of experiments that have been reported to very good precision (obviously not all to the extra-ordinary precision of this measurement). There are no longer any “free parameters” in the SM, in the sense that each one has been constrained by at least one experiment by now. Also, in complicated processes like this one, multiple parameters could make an effect on the observed value…

ah, well it will be interesting to see how the theorists resolve this!

Re: Particle mystery: physicists confirm the muon is more magnetic than predicted

#172

Post by 6gvONxR4sf7o »

whatshisface wrote: post #113
ssivark wrote: post #32

Earlier quoted context omitted.

To clarify, for those not familiar with this topic, this experiment is making measurements at such exquisite precision that even the calculations for the theoretical prediction are extremely non-trivial and require careful estimation of many many pieces which are then combined. Which is to say that debugging the theoretical prediction is (almost) as hard as debugging the experiment. So I would expect the particle phy…

If the theoretical prediction can't be calculated until the experiment is done that motivates the choices of what and what not to approximate, is it really a prediction?

Sometimes it's like unit tests, where you might get the test itself wrong at first, but that still helps you get closer and write better tests.

Re: Particle mystery: physicists confirm the muon is more magnetic than predicted

#174

Post by jl6 »

schmorptron wrote: post #96
BlueTemplar wrote: post #60

Earlier quoted context omitted.

Godel kind of proved that about Mathematics.

That sounds wild, do you have a link where I can read more about this, or is wikipedia fine to learn about it?

Axioms are the foundational assumptions from which formal systems of mathematics are built. Some systems of axioms are unable to prove the truth or falsity of some statements within that system. But you can add such statements to your set of axioms to form a new, larger formal system, which in turn has other indeterminate statements, and so on, thus building, in GP’s terms, an infinite playground of mathematics.

Book recommendation: Gödel, Escher, Bach by Douglas Hofstadter.

Re: Particle mystery: physicists confirm the muon is more magnetic than predicted

#175

Post by gfodor »

ssivark wrote: post #134
platz wrote: post #46

Earlier quoted context omitted.

it's not good to cherry-pick paragraphs from the whole artile. > But as the Brookhaven team accrued 10 times more data, their measurement of the muon’s g-factor stayed the same while the error bars around the measurement shrank. The discrepancy with theory grew back to three sigma by the time of the experiment’s final report in 2006.

No, the essence of my point is that the number of sigmas is meaningless when you have a systematic error — in either the experiment or the theoretical estimate — all that the sigmas tell you is that the two are mismatched. If a mistake could happen once, a similar mistake could easily happen again, so we need to be extremely wary of taking the sigmas at face value. (Eg: the DAMA experiment reports dark matter detecti…

“A similar mistake could happen again”

“Similar” is doing a lot of work there - what constitutes similar basically dictates if error correction has any future proofing benefits or none at all.

Re: Particle mystery: physicists confirm the muon is more magnetic than predicted

#176

Post by eevilspock »

> "The concordance shows the old result was neither a statistical fluke nor the product of some undetected flaw in the experiment, says Chris Polly, a Fermilab physicist and co-spokesperson for the g-2 team. “Because I was a graduate student on the Brookhaven experiment, it was certainly an overwhelming sense of relief for me,” he says."

A committed scientist should worry about having such feelings, even though it is very human. It represents a possible source of non-independence of tests and of scientific bias.

Re: Particle mystery: physicists confirm the muon is more magnetic than predicted

#178

Post by goatcode »

dylan604 wrote: post #156
goatcode wrote: post #71

Earlier quoted context omitted.

Weird. This must have changed in the past 10 years or so, since I've been out of college.

It's something you never get used to. As you get older, this will just keep happening. We used to put commas before the last item in a list back in like the stone ages when I was in school. My SAT score looked really lame for a bit of time when those suddenly changed.

I understand the grumpy old person archetype now. I feel like I've been one for a long time, but it's really hitting home over the past decade.

Re: Particle mystery: physicists confirm the muon is more magnetic than predicted

#179

Post by raincom »

whatshisface wrote: post #113
ssivark wrote: post #32

Earlier quoted context omitted.

To clarify, for those not familiar with this topic, this experiment is making measurements at such exquisite precision that even the calculations for the theoretical prediction are extremely non-trivial and require careful estimation of many many pieces which are then combined. Which is to say that debugging the theoretical prediction is (almost) as hard as debugging the experiment. So I would expect the particle phy…

If the theoretical prediction can't be calculated until the experiment is done that motivates the choices of what and what not to approximate, is it really a prediction?

That's what Duhem-Quine thesis in the philosophy of sciences is. The thesis is that "it is impossible to test a hypothesis in isolation, because an empirical of the hypothesis requires one or more auxiliary/background assumptions/hypotheses".

Re: Particle mystery: physicists confirm the muon is more magnetic than predicted

#180

Post by dukwon »

tompagenet2 wrote: post #177

Genuine question from ignorance. Is this related to this work at CERN? https://www.theguardian.com/science/2021/mar/23/large-hadron...

Maybe. There are plenty of attempts to explain g-2 and LFUV in B decays in one go.

But really there's no way to know for sure yet.

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