tag:blogger.com,1999:blog-13869903.post7552785038390657771..comments2021-05-17T11:19:16.716-05:00Comments on nanoscale views: Place your bets. Muon g-2....Douglas Natelsonhttp://www.blogger.com/profile/13340091255404229559noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-13869903.post-57563918952224719662021-04-18T22:42:59.484-05:002021-04-18T22:42:59.484-05:00Anon, fixed. That’s what I get for being in a hur...Anon, fixed. That’s what I get for being in a hurry.Douglas Natelsonhttps://www.blogger.com/profile/13340091255404229559noreply@blogger.comtag:blogger.com,1999:blog-13869903.post-77018490696129838072021-04-17T03:08:47.771-05:002021-04-17T03:08:47.771-05:00A muon antineutrino? Shouldn't it be an electr...A muon antineutrino? Shouldn't it be an electron antineutrino and a muon neutrino, to conserve lepton numbers?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-13869903.post-42233848032646823852021-04-09T17:03:35.370-05:002021-04-09T17:03:35.370-05:00https://www.youtube.com/watch?v=92OHzl3vUBghttps://www.youtube.com/watch?v=92OHzl3vUBgAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-13869903.post-5369960620578459922021-04-09T16:10:44.264-05:002021-04-09T16:10:44.264-05:00Perhaps useful to quote Peter Woit on this:
"...Perhaps useful to quote Peter Woit on this:<br /><br />"The problem is that while the situation with the experimental value is pretty clear (and uncertainties should drop further in coming years as new data is analyzed), the theoretical calculation is a different story. It involves hard to calculate strong-interaction contributions, and the muon g-2 Theory Initiative number quoted above is not the full story. The issues involved are quite technical and I certainly lack the expertise to evaluate the competing claims. To find out more, I’d suggest watching the first talk from the FNAL seminar today, by Aida El-Khadra, who lays out the justification for the muon g-2 Theory Initiative number, but then looking at a new paper out today in Nature from the BMW collaboration. They have a competing calculation, which gives a number quite consistent with the experimental result [...]"Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-13869903.post-82855601839305359722021-04-07T15:39:03.491-05:002021-04-07T15:39:03.491-05:00So, the experimental value seems to be consistent ...So, the experimental value seems to be consistent with the BNL number, despite numerous changes in the experimental setup, which is good. The data collection from runs 2-4 will shrink the statistical uncertainties by quite a bit. The question is then "what is the correct theoretical prediction for comparison?" As mentioned in <a href="https://www.quantamagazine.org/muon-g-2-experiment-at-fermilab-finds-hint-of-new-particles-20210407/" rel="nofollow">this typically high quality article</a> by Natalie Wolchover, and further in <a href="http://realselfenergy.blogspot.com/2020/03/muon-g-2-lattice-salad.html" rel="nofollow">this blog post</a>, there is tension between theory calculations of the hadron contribution that are computed using "R-ratios" (which feeds in experimentally measured cross-sections plus the optical theorem), and <i>pure</i> theory calculations based on lattice QCD methods (which include certain approximations). The "BMW" result is a new version of the latter, and it's closer to the experimental value, though quite far from all of the R-ratio approaches. <br /><br />Even aside from the experiment, if the R-ratio analysis is all correct, and the lattice QCD calculations are also all correct and complete, and they still disagree, then there has to be missing physics somewhere....Douglas Natelsonhttps://www.blogger.com/profile/13340091255404229559noreply@blogger.comtag:blogger.com,1999:blog-13869903.post-32556503962136185822021-04-07T14:52:44.344-05:002021-04-07T14:52:44.344-05:00Kind of disappointing that after so many years the...Kind of disappointing that after so many years the result is still not conclusive enough to say much.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-13869903.post-11772888058779563552021-04-06T00:21:48.764-05:002021-04-06T00:21:48.764-05:00From the general attitude around UChicago, my bet ...From the general attitude around UChicago, my bet is yes they have a 5 sigma (or better) deviation from SM. <br /><br />But I admit I am biased. I really hope that they find something new here, the proton mass puzzle in recent years was a bit of a letdown. Precision measurements are a lot more promising to me at least than higher energy collisions, so i personally want to seee this continue. Anonymousnoreply@blogger.com