There's much hanging on the unpredicted wobble. Muons, heavier cousins of electrons, do not behave as predicted when shot through an intense magnetic field, a lab in Illinois reports. In wobbling faster than expected, scientists say, they are raising tantalising questions about the accepted understanding of the basic laws of particle physics, the "standard model" which describes the particles (currently 17) and forces that govern the subatomic world.
Mainstream thinking suggests that all of the forces we experience can be reduced to just four categories: gravity, electromagnetism, and, shaping the behaviour of sub-atomic particles, the strong force and the weak force. The muon wobble suggests a fifth force which could provide an explanation for such mysteries as the speeding up of the expanding universe and the nature of dark matter, the unseen stuff that astronomers say makes up one-quarter of the mass of the universe.
Strange behaviour
Results announced last week from the Muon g-2 experiment at the Fermi National Accelerator Laboratory, or Fermilab, in Batavia – a team of 200 physicists from seven countries – appear to have replicated successfully a 20-year-old experiment on muons' strange behaviour and their divergence from the standard model that had remained unexplained. Separately, reports from the Large Hadron Collider at Cern on the Swiss-French border on the decay of unstable B mesons into muons and electrons this week have also thrown up doubts about the model.
At a seminar and news conference last week, Fermilab physicist Dr Chris Polly pointed to a graph displaying white space where their findings deviated from the theoretical prediction. "We can say with fairly high confidence, there must be something contributing to this white space. What monsters might be lurking there?"
The work and its promising implications are far from conclusive, but scientists have compared it to the much-heralded discovery in 2012 of the Higgs boson, a particle that imbues other particles with mass. The fleeting quantum world of the muon may be giving up its secrets.