nature: The excess of photons produced by particle collisions at the Large Hadron Collider (LHC) has kept physicists abuzz since it was discovered three months ago. by Davide Castelvecchi and Elizabeth Gibney
'Now the use of fresh data by one LHC experiment has made the signal slightly more statistically significant — but it still falls well short of the certainty needed to claim a discovery.
'In December, physicists announced that they had seen an excess of pairs of γ-ray photons with a combined energy of around 750 gigaelectronvolts. The data came from ATLAS and CMS, the two largest detectors at the 27-kilometre-circumference LHC at CERN, the European particle-physics laboratory near Geneva, Switzerland.
'The excess seen by the CMS experiment has now become slightly more significant, owing to a fresh analysis reported on 17 March at a conference in La Thuile, Italy. But to the disappointment of many, the analysis presented by ATLAS on the same day, which did not contain new data, did little to change the status of the mysterious excess. In fact, the significance seen by ATLAS went down a bit as a result of the analysis, which was a more conservative interpretation of the data-set than previously, says Marco Delmastro, the physicist at the CNRS Theoretical Physics Laboratory in Annecy-le-Vieux, France who presented the ATLAS results.'