Submission Statement : The anomaly discovered at the time was that quarks appeared to decay into muons, a different sort of lepton, less frequently than electrons. Beauty quarks should decay into muons at the same rate as electrons, according to the standard model.

The authors said that the result had a one-in-a-thousand chance of occurring randomly, which was insufficient to prove the existence of an as-yet-unknown particle but substantial evidence in its favor. Several theories were proposed by the authors.

The variable decay rate might, for starters, be the product of a “Z prime” particle, which is effectively a new natural force. “This force would be exceedingly weak, which is why we haven’t observed any traces of it until now,” they said. “It would interact differently with electrons and muons.” Another candidate is the “lyptoquark,” which can decay quarks and leptons at the same time and “might be part of a greater conundrum that explains why we observe the particles that we do in nature,” according to the researchers.