The Idea Initiative determined to not embrace BMW’s worth of their official estimate for just a few causes. The information-driven strategy has a barely smaller error bar, and three totally different analysis teams independently calculated the identical factor. In distinction, BMW’s lattice calculation was unpublished as of final summer season. And though the consequence agrees properly with earlier, much less exact lattice calculations that additionally got here out excessive, it hasn’t been independently replicated by one other group to the identical precision.
The Idea Initiative’s choice meant that the official theoretical worth of the muon’s magnetic second had a 3.7-sigma distinction with Brookhaven’s experimental measurement. It set the stage for what has turn out to be probably the most anticipated reveal in particle physics because the Higgs boson in 2012.
A month in the past, the Fermilab Muon g-2 crew introduced that they might current their first outcomes on April 7. Particle physicists had been ecstatic. Laura Baudis, a physicist on the College of Zurich, stated she was “counting the times,” after anticipating the consequence for 20 years. “If the Brookhaven outcomes are confirmed by the brand new experiment at Fermilab,” she stated, “this may be an unlimited achievement.”
And if not—if the anomaly had been to vanish—some within the particle physics group feared nothing lower than “the top of particle physics,” stated Stöckinger. The Fermilab g-2 experiment is “our final hope of an experiment which actually proves the existence of physics past the usual mannequin,” he stated. If it failed to take action, many researchers would possibly really feel that “we now hand over and now we have to do one thing else as an alternative of researching physics past the usual mannequin.” He added, “Actually talking, it could be my very own response.”
The 200-person Fermilab crew revealed the consequence to themselves solely six weeks in the past in an unveiling ceremony over Zoom. Tammy Walton, a scientist on the crew, rushed house to catch the present after working the night time shift on the experiment, which is at the moment in its fourth run. (The brand new evaluation covers information from the primary run, which makes up 6 % of what the experiment will ultimately accrue.) When the all-important quantity appeared on the display screen, plotted together with the Idea Initiative’s prediction and the Brookhaven measurement, Walton was thrilled to see it land increased than the previous and just about smack dab on prime of the latter. “Individuals are going to be loopy excited,” she stated.
Papers proposing varied concepts for brand new physics are anticipated to flood the Arxiv within the coming days. But past that, the long run is unclear. What was as soon as an illuminating breach between principle and experiment has been clouded by a far foggier conflict of calculations.
It’s attainable that the supercomputer calculation will transform unsuitable—that BMW ignored some supply of error. “We have to have an in depth have a look at the calculation,” El-Khadra stated, stressing that it’s too early to attract agency conclusions. “It’s pushing on the strategies to get that precision, and we have to perceive if the best way they pushed on the strategies broke them.”
That will be excellent news for followers of latest physics.
Curiously, although, even when the data-driven technique is the strategy with an unidentified downside underneath the hood, theorists have a tough time understanding what the issue may very well be aside from unaccounted-for new physics. “The necessity for brand new physics would solely shift elsewhere,” stated Martin Hoferichter of the College of Bern, a number one member of the Idea Initiative.
Researchers who’ve been exploring attainable issues with the data-driven technique over the previous 12 months say the information itself is unlikely to be unsuitable. It comes from many years of ultraprecise measurements of 35 hadronic processes. However “it may very well be that the information, or the best way it’s interpreted, is deceptive,” stated Andreas Crivellin of CERN and different establishments, a coauthor (together with Hoferichter) of one paper finding out this risk.