Meanwhile, in 2020, a group of 170 experts known as the Muon g-2 Theory Initiative released a new consensus value of the theoretical value of the magnetic moment of the muon, based on three years of workshops and calculations using the standard model. This response reinforced the initial divergence reported by Brookhaven.
Reached by phone Monday, Aida X. El-Khardra, a physicist at the University of Illinois and co-chair of the Muon g-2 Theory Initiative, said she was unaware of the result Fermilab would announce two days later. – and she didn’t want to, for fear of being tempted to fake at a conference scheduled just before the official unveiling on Wednesday.
“I have never had the feeling of sitting on hot coals before,” said Dr El-Khadra. “We have been waiting for this for a long time.”
On the day of Fermilab’s announcement, another group, using a different technique known as a lattice calculus to calculate the muon’s magnetic moment, concluded that there was no discrepancy between the measurement of Brookhaven and the standard model.
“Yes, we claim that there is no discrepancy between the Standard Model and the Brookhaven result, no new physics,” said Zoltan Fodor of Pennsylvania State University, one of the authors of a report published in Nature Wednesday.
Dr El-Khadra, who was familiar with this work, called it “an astonishing calculation, but not conclusive”. She noted that the calculations involved were horribly complicated, having to account for every possible way a muon could interact with the universe, and requiring thousands of individual sub-calculations and hundreds of hours of supercomputer time.
These lattice calculations, she said, needed to be checked against independent results from other groups to rule out the possibility of systematic errors. For now, the Theory Initiative calculation remains the standard by which measurements will be compared.