19 April 2017
The Standard Model of particle physics is the theory that predicts how particles and forces behave, however it is incomplete, not including gravity, nor explaining dark matter that makes up most of the Universe. More data is needed before LHCb scientists can definitively confirm they’ve found a crack in the Standard Model of particle physics, but this result strengthens similar indications from earlier studies.
Dr. Simone Bifani from the University of Birmingham presented the new results in a seminar at CERN. "The measurements represent a milestone for the LHCb collaboration. When we update the analysis to include data recorded during Run 2 we have the potential to make the first observation of physics beyond the Standard Model at the LHC."
In this study, the LHCb collaboration looked at the decays of B0 mesons to an excited kaon and a pair of electrons or muons. The muon is 200 times heavier than the electron, but in the Standard Model its interactions are otherwise identical to those of the electron, a property known as lepton universality. Lepton universality predicts that, up to a small and calculable effect due to the mass difference, electron and muons should be produced with the same probability in this specific B0 decay. LHCb finds instead that the decays involving muons occur less often.
"Lepton universality is a basic feature of the Standard Model - break it, and you've blown our existing understanding of particle physics wide open,” said Professor Tara Shears from the University of Liverpool, a leading scientist working on the LHCb experiment. “This result gives us a tantalising glimpse of what might be out there. We need to analyse more data to see this behaviour is real or a statistical quirk, but, with the high quality data LHC has delivered and the fantastic performance of our particle detectors, we're ready for it."
Professor Tim Gershon from the University of Warwick and spokesperson for LHCb-UK added "The mood is one of cautious excitement -- no-one is popping any champagne corks yet. Detailed understanding of these deviations requires a long-term programme of measurements that we are now planning. Work is ongoing towards LHCb detector upgrades that will enable the increased sensitivity that is required."