CERN announces discovery of Higgs boson-like particle
Twenty-seven kilometres of ring, deep underground near Geneva. For more than two years, beams of protons had been accelerated to almost the speed of light and smashed into each other inside it. Nobody in the auditorium had slept much.
At CERN, outside Geneva, the numbers finally held. CMS, one of two enormous detectors at the Large Hadron Collider, had reached a local significance of 4.9 sigma at a mass of 125.3 GeV. ATLAS, the other detector, designed and built by thousands of people over two decades, had come in at five sigma. Two machines, two answers, and they matched.
The particle had been hunted for almost fifty years. It was the last thing the standard model of matter still predicted and nobody had ever seen, the missing piece thought to hand every other particle its mass. Someone had called it the God particle, and the name annoyed the physicists who had given their careers to finding it. In December 2011, the ATLAS and CMS teams had each reported tantalising hints of a Higgs-like boson, though those readings carried only three sigma of confidence, enough to quicken the pulse and not enough to say the word out loud.
On the morning of July 4, 2012, a single seminar links the CERN auditorium to a hall in Melbourne, where the International Conference on High Energy Physics is already underway. The two collaborations have spent the run kept blind to each other's numbers, each analysing its own data so that neither team could nudge its result toward the other's answer. One after the other, they read out what they have found.
ATLAS puts its local significance at five sigma, the threshold physicists hold before they will use the word discovery, a less than one-in-a-million chance the signal is only a fluke. Both detectors settle on the same object: a particle with a mass of 125 to 126 gigaelectronvolts, roughly 130 times the mass of a proton. Two experiments, built and run by separate teams, arrive at the same place along the mass scale. It is the most massive boson anyone has ever seen.
The theory itself was old by now. Robert Brout, one of the physicists who had first worked out how the particle could give mass to matter, had died in 2011, a year before the detectors settled on their number. He did not hear the announcement.
By the end of the seminar, both machines had converged on a single object near 125 gigaelectronvolts, the heaviest boson yet observed, and the last prediction of the standard model that no one had ever seen was no longer only on paper.










