Intriguing excess of top-quark pairs hints at discovery of smallest composite particle

The CMS collaboration at CERN has observed an unexpected feature in data produced by the Large Hadron Collider (LHC), which could point to the existence of the smallest composite particle yet observed. The result, reported at the Rencontres de Moriond conference in the Italian Alps this week, suggest that top quarks—the heaviest and shortest lived of all the elementary particles—can momentarily pair up with their antimatter counterparts to produce an object called toponium.