An intriguing signal from the Large Hadron Collider (LHC) might prove to be the crack that prises apart the standard model — physicists’ current best description of how matter and forces interact.

Analysis of data gathered during 2011–12 at the collider at CERN, Europe’s particle-physics laboratory near Geneva, Switzerland, suggests that in particular decays, short-lived particles called B-mesons create taus more frequently than they create muons. (Taus and muons are heavier cousins of electrons.) But the standard model says that once the particles’ mass differences are taken into account, the decays should occur at exactly the same rate. The finding will be published in Physical Review Letters this month (and has been on the arXiv1 pre-print server since June).

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