LHCb Collaboration Reports Evidence of Rare B0 Meson Decay Consistent with Standard Model
Researchers at CERN's LHCb experiment have observed a rare decay of B0 mesons into muon pairs, with a measured rate that aligns with Standard Model predictions.
Physicists working with the LHCb Collaboration at CERN’s Large Hadron Collider have announced evidence for a rare decay of the B0 meson into a pair of muons. The decay, predicted to occur roughly once in every ten billion B0 decays, was observed with a statistical significance of 3.0 standard deviations in the latest data set, rising to 3.2 standard deviations when combined with earlier LHCb results. The measured branching fraction for the new data alone is about 1.26 in 10 billion, compared with the Standard Model expectation of 1.03 in 10 billion; the combined result is 1.14 in 10 billion.
“What we found in these latest results is an incredibly rare decay of one of these beauty particles, where it turns into two even smaller particles called muons,” said Dr. Harry Cliff of the University of Cambridge’s Cavendish Laboratory.
The team also reported the most precise determination to date of the related decay of the B0s meson, finding a branching fraction of 3.31 in a billion against a Standard Model prediction of 3.66 in a billion, and measured its effective lifetime at 1.42 picoseconds (statistical uncertainty 0.18 picoseconds), or 1.60 picoseconds when combined with previous data.
“Physicists have been chasing this decay for more than forty years,” said Dr. Marco Santimaria of the INFN Laboratori Nazionali di Frascati. “Extreme precision is required to pick the muons out of the overwhelming background.”
“LHCb is a great success story of CERN, and one in which Oxford has been proud to play a leading role, dating back to the inception of the project in 1995,” said Professor Guy Wilkinson of the University of Oxford. “Today’s announcement ushers in a new era of discovery for the experiment, and vividly demonstrates the increased sensitivity we have attained in our quest to probe beyond our current understanding of physics at the most fundamental level.”
“This result showcases the extraordinary capabilities of LHCb to probe nature at the fundamental level,” added Professor Tim Gershon of the University of Warwick.