The scientists at the Fermilab Collider Detector (CDF) in Illinois have found only a tiny difference in the mass of the W Boson compared with what the theory says it should be - just 0.1%. But if confirmed by other experiments, the implications are enormous. The so-called Standard Model of particle physics has predicted the behaviour and properties of sub-atomic particles with no discrepancies whatsoever for fifty years. Until now.
CDF's other co-spokesperson, Prof Georgio Chiarelli, from INFN Sezione di Pisa, told BBC News that the research team could scarcely believe their eyes when they saw the results.
"No-one was expecting this. We thought maybe we got something wrong." But the researchers have painstakingly gone through their results and tried to look for errors. They found none.
The result, published in the journal Science, could be related to hints from other experiments at Fermilab and the Large Hadron Collider at the Swiss-French border. These, as yet unconfirmed results, also suggest deviations from the Standard Model, possibly as a result of an as yet undiscovered
fifth force of nature at play.