Sharing disappointing results with a world of researchers working to find what they hope will be the “discovery of the century” isn’t an easy task, but that is what Penn State theoretical physicist Zoltan Fodor and his international research group did five years ago with their extensive calculation of the strength of the magnetic field around the muon —a sub-atomic particle similar to, but heavier than, an electron. At the time, their finding was the first to close the gap between theory and experimental measurements, bringing it in line with the Standard Model, the well-tested physics theory that has guided particle physics for decades.

Earlier on the same day, after almost 20 years, a new experimental result was also published showing a strong discrepancy between the theory and the experiment. This was interpreted by most physicists as a sign of new physics, and many physicists shared some skepticism of Fodor’s results and hoped that with more research, the other groups’ result would ring true.

Why? Twenty-four years ago, in an experiment at Brookhaven National Laboratory, physicists detected what seemed to be a discrepancy between measurements of the muon’s “magnetic moment”—the strength of its magnetic field—and theoretical calculations of what that measurement should be, raising the tantalizing possibility of undiscovered physical particles or forces. They reported that the muon was more magnetic than was predicted by the Standard Model.