However, the calculations are still preliminary and could differ if applied beyond the current window. “We don’t yet know if the lattice results from other collaborations agree with the BMW result for the extended calculation,” says Aida El-Khadra, a theorist at the University of Illinois at Urbana-Champaign, who is also part of a lattice QCD working group is.
In addition, the experimental result of “Muon g-2” is still higher than the value calculated by the lattice QCD, so it is too early to conclude that the Standard Model was correct all along. The researchers at the Fermilab experiment expect to publish an updated value for the magnetic moment next year, but “even if the gap between theoretical prediction and experiment were to get smaller – even if it was only half as big – it would still be one clear deviation«, says the Mainz physicist Hartmut Wittig.
“It’s hard to imagine that all our lattice simulations were wrong”(Christopher Aubin, theoretical particle physicist)
And even if the lattice QCD and the experimental measurements ended up being the same, researchers would still have to explain why the 2020 consensus paper was so off the mark, says Sven Heinemeyer, a theoretical physicist at CERN, the European laboratory for particle physics near Geneva in Switzerland.
At the moment, the scientists can only scratch their heads. “It’s hard to imagine that all of our lattice simulations were wrong,” says Christopher Aubin. But it’s also hard to imagine that the data-driven calculations of 2020 have all gone wrong, he says.
Nevertheless, it is already clear that lattice QCD will have a significant impact on the question of muon magnetism, says Giusti. “This calculation is really exciting, and whatever the answer, it will be crucial.”