Hints of new particle in LHC data grow somewhat stronger

Nature : Last December, the ATLAS and CMS detector teams at CERN’s Large Hadron Collider (LHC) announced that they had seen a bump in the data that indicated the possibility of a new particle with a mass around 750 GeV. Both teams found the signal in the production of pairs of gamma-ray photons, but neither detector approached the 5 σ confidence level necessary to confirm a discovery. A secondary analysis of the data presented on 17 March at a conference in La Thuile, Italy, has somewhat increased the confidence level. The CMS reanalysis included 23% more data and a recalibration to account for radiation affecting the measurements. The resulting signal increased from a 1.2 σ to a 1.6 σ confidence level. A reanalysis of the ATLAS data saw a drop in confidence, though not enough of one to outweigh the increase in the CMS data. A new particle at 750 GeV is not predicted by any widely accepted theories, which makes the potential discovery so exciting. LHC researchers believe they will have enough data by midsummer to declare whether the signal is a new particle or just a statistical fluctuation.