The Theory Initiative decided not to include the BMW value in its official estimate for several reasons. The data-driven approach has a slightly smaller error bar, and three different research groups calculate the same thing independently. In contrast, BMW’s network account has not been released as of last summer. Although the result agrees well with early, less-accurate grid calculations that were also high, it was not independently replicated by another group with the same accuracy.
The theoretical initiative decision implied that the formal theoretical value of the muon’s magnetic moment had a difference of 3.7 sigma with the experimental Brookhaven measurement. It paved the way for what has become the most anticipated detection in particle physics since the Higgs boson in 2012.
A month ago, the Fermilab Muon g-2 team announced that they will be presenting their first results on April 7th. Particle physicists were ecstatic. Laura BodiceThe University of Zurich physicist said she was “counting the days” after predicting the result for 20 years. She said, “If Brookhaven’s results are confirmed with the new trial in Fermilab, that would be a colossal achievement.”
And if that wasn’t the case – if the anomalies disappeared – then some in the particle physics community feared nothing less than “the end of particle physics,” says Stockinger. He said the Fermilab g-2 experiment is “our last hope for an experiment that really proves physics beyond the standard model.” If it fails to do so, many researchers may feel that “we are giving up now and have to do something else instead of researching physics beyond the standard model.” He added, “Frankly, it might be my reaction.”
The 200-person Fermilab team revealed the result for themselves just six weeks ago at the unveiling party for Zoom. Tammy WaltonOne of the scientists on the team rushed home to watch the show after working on the night shift on the experiment, which is currently in its fourth round. (The new analysis covers data from the first run, which makes up 6 percent of what the experiment will eventually get.) When the hugely important number appeared on screen, which was plotted alongside the initiative’s theoretical prediction and Brookhaven scale, Walton was thrilled to see it land higher. Of the former and greatly hitting above the latter. “People will be crazy excited,” she said.
Papers proposing various ideas for new physics are expected to overwhelm Arxiv in the coming days. But then, the future is unclear. What was once a luminous breach between theory and experiment has been overshadowed by an even more hazy struggle of accounts.
It’s possible that the supercomputer’s calculation will turn out to be wrong – because BMW has omitted some sources of error. “We need to take a close look at the accounts,” Khadra said, stressing that it was too early to draw firm conclusions. “They are pushing the methods to have that accuracy, and we need to understand whether the way they push the methods breaks them.”
This will be good news for fans of the new physics.
Interestingly, even if the data-driven method is the approach with an indeterminate problem under the hood, theorists find it difficult to understand what the problem could be other than the new, unexamined physics. “The need for new physics will only shift elsewhere,” he said. Martin Hofercher From the University of Bern, lead member of the Theory Initiative.
Researchers who have been exploring potential issues using the data-driven method over the past year say the data itself is unlikely to be wrong. It comes from decades of super-accurate measurements of 35 hadronic processes. But “the data or the way it is interpreted could be misleading.” Andreas Krevelin From CERN and other institutions, he is a co-author (along with Hoferichter) for One sheet Study this possibility.