In the Dark

Via a characteristically garbled piece in the Grauniad, bizarrely entitled Scientists may be on brink of discovering fifth force of nature, I found out that there has been an announcement of a new measurement of the anomalous magnetic dipole moment – known to its friends as (g-2) – of the muon. This new measurement is consistent with one made a couple of years ago, but with a smaller range of uncertainty. It’s an impressive result from an experimental point of view.

There is a news item explaining the new result here, which says

Precision test of particle’s magnetism confirms earlier shocking findings — but theory might not need a rethink after all.

That’s pretty much the opposite of what the Guardian piece says.

There’s also a video produced by the Fermilab Muon g-2 team that explains what has changed from 2021 to now:

My own view is that these recent experimental measurements of g-2, which seem to be a bit higher than theorists expected, can be straightforwardly reconciled with the predictions of the standard model of particle physics by simply adopting a slightly lower value of 2 in the theoretical calculations.

P.S. The classical value is of course  g-2 ≈ 7.81 m s^-2.

This entry was posted on August 14, 2023 at 3:37 pm and is filed under The Universe and Stuff with tags anomalous magnetic moment, g-2, Muon g-2, muon magnetic moment. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.