The Theory Initiative determined to not embody BMW’s worth of their official estimate for just a few causes. The data-driven method 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 In distinction, BMW’s lattice calculation was unpublished as of final summer season.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 outcome 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 Theory Initiative’s determination 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 for the reason that Higgs boson in 2012.
The Revelations
A month in the past, the Fermilab Muon g-2 workforce introduced that they’d current their first outcomes on April 7. Particle physicists have been ecstatic. Laura Baudis, a physicist on the University of Zurich, stated she was “counting the days,” after anticipating the outcome for 20 years. “If the Brookhaven results are confirmed by the new experiment at Fermilab,” she stated, “this would be an enormous achievement.”
And if not—if the anomaly have been to vanish—some within the particle physics group feared nothing lower than “the end of particle physics,” stated Stöckinger. The Fermilab g-2 experiment is “our last hope of an experiment which really proves the existence of physics beyond the standard model,” he stated. If it failed to take action, many researchers may really feel that “we now give up and we have to do something else instead of researching physics beyond the standard model.” He added, “Honestly speaking, it might be my own reaction.”
The 200-person Fermilab workforce revealed the outcome to themselves solely six weeks in the past in an unveiling ceremony over Zoom. Tammy Walton, a scientist on the workforce, rushed residence to catch the present after working the night time shift on the experiment, which is at the moment in its fourth run. (The new evaluation covers knowledge from the primary run, which makes up 6 p.c of what the experiment will finally accrue.) When the all-important quantity appeared on the display screen, plotted together with the Theory Initiative’s prediction and the Brookhaven measurement, Walton was thrilled to see it land larger than the previous and just about smack dab on high of the latter. “People are going to be crazy excited,” she stated.
Papers proposing varied concepts for new physics are anticipated to flood the Arxiv within the coming days. Yet past that, the longer term 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 change into flawed—that BMW neglected some supply of error. “We need to have a close look at the calculation,” El-Khadra stated, stressing that it’s too early to attract agency conclusions. “It is pushing on the methods to get that precision, and we need to understand if the way they pushed on the methods broke them.”
That can be excellent news for followers of latest physics.
Interestingly, although, even when the data-driven technique is the method with an unidentified downside beneath the hood, theorists have a tough time understanding what the issue may very well be aside from unaccounted-for new physics. “The need for new physics would only shift elsewhere,” stated Martin Hoferichter of the University of Bern, a number one member of the Theory 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 flawed. It comes from a long time of ultraprecise measurements of 35 hadronic processes. But “it could be that the data, or the way it is interpreted, is misleading,” stated Andreas Crivellin of CERN and different establishments, a coauthor (together with Hoferichter) of one paper finding out this risk.