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• CommentRowNumber1.
• CommentAuthorUrs
• CommentTimeFeb 6th 2018
• (edited Feb 6th 2018)

there is an old article (Berends-Gastman 75) that computes the 1-loop corrections due to perturbative quantum gravity to the anomalous magnetic moment of the electron and the muon. The result turns out to be independent of the choice of (“re”-)normalization (hence what they call “finite”).

I have added a remark on this in the $(g-2)$-entry here and also at quantum gravity here.

• CommentRowNumber2.
• CommentAuthorUrs
• CommentTimeJan 2nd 2019

added a paragraph with literature pointers on the latest discrepancies between theory and experiment (here)

• CommentRowNumber3.
• CommentAuthorUrs
• CommentTimeJan 16th 2019

added pointer to possible explanation of the anomaly in the anomalous magnetic moments via leptoquarks

• CommentRowNumber4.
• CommentAuthorUrs
• CommentTimeJan 23rd 2019

added the table by Lyons (here), kindly pointed out by David C., which argues that the detection-threshold for anomalies in the anomalous magnetic moment of the muon should be $4 \sigma$ instead of the conventional $5 \sigma$ – which would mean that the current experimental significance should already be counted as detection.

• CommentRowNumber5.
• CommentAuthorDavid_Corfield
• CommentTimeJan 24th 2019

Looking over some of the writings by experimentalists, you see how sensitive degrees of plausibility are to new information, theoretical or experimental. E.g., for this anomaly on this page, Dorigo seems to have gone from enthusiasm Muon G-2: The Anomaly That Could Change Physics, And A New Exciting Theoretical Development to doubt Gravitational Effects Explain Muon Magnetic Moment Anomaly Away!! in a few months.

Then people in comments of the second post cast doubt on this explaining away. Is that largely agreed now that GR doesn’t explain away the anomaly?

• CommentRowNumber6.
• CommentAuthorUrs
• CommentTimeJan 24th 2019

Yes, that GR argument was nonsense, and both the people running the experiment as well as independent theorists were very quick to point out that it couldn’t possibly be true, even without looking at the details. Then a little later somebody identified the erroneous step in the computation (that was somebody from Zagreb active on PhysicsForums, incidentally, he wrote a 2 page article about it.).

There was a comprehesive sum-up of the whole situation recently on the arXiv, but now I don’t have the link.

But generally I want to insist again that it is crucially important in science to keep experimental results strictly independent of theoretical expectations. Otherwise we fall back into darkness to before the age of enlightment.

Our “excitement” and all these soft human factors that you tend to stress will depend on all kinds of things, but before we even start getting into that, we need to have an idea with which independent objective certainty experimentalists are seeing a signal or not.

• CommentRowNumber7.
• CommentAuthorDavid_Corfield
• CommentTimeJan 24th 2019

What is it about this topic that makes for this strange gap between us? I just don’t recognise your way of describing what I say.

Our “excitement” and all these soft human factors that you tend to stress…

What is that about? When did I ever speak of excitement?

Did you know before this conversation that there is a difference between global and local p-values due to the Look Elsewhere Effect? Is that one of my “soft human factors”, or is it that you had to learn something about data analysis? I hope you’ve picked something up from some of these articles we’ve looked at. I certainly have.

But something I haven’t shifted a jot on is that doing the best with the information available is a far from simple process. There are many components to this information and typically this needs a team of experts to bring their distributed expert knowledge to the table. Dorigo errs above by moving too quickly and not waiting for the theoreticians to adjudicate. He should have had higher prior expectation that that theoretical explaining away would be found to be spurious. He wouldn’t have had to wait long in that case.

We should always look to use the best expertise we can access so as to have the most accurate expectations that: the instruments are working as intended, that systematic errors have been reduced, that the predictions are done correctly, that we understand correctly how the search for a signal is conducted … This has nothing to do with “excitement” and it’s not “soft”.

What does the “hardness” of a sigma level amount to if the “soft” understanding of the experiment changes? When you heard in 2011 of the signal for neutrinos travelling faster than light, what did their “hard” $6 \sigma$ (p. 22) count for? Wasn’t it overwhelmingly likely that something had been overlooked in the measurement process? Isn’t the “hardness” in this case coming from a reasonable unwillingness on theoretical grounds to give up on the speed of light as greatest velocity? But are you going to call that unwillingness “soft” and “human”? Or is not something that any rational (unexcited) theoretician will maintain given what was known in 2011?