CERN Detects Excited Bc*+ Meson at the LHC

ATLAS physicists at CERN observed the excited Bc*+ meson, a heavy-quark bound state (charm quark with a bottom antiquark), produced in high-energy proton-proton collisions at the LHC. The Bc*+ rapidly decays to a Bc+ meson and a photon, which was identified indirectly when the photon converted into an electron–positron pair in the detector. The measured mass difference between Bc*+ and Bc+ is 64.5 ± 1.4 MeV, consistent with theoretical expectations and providing new data to refine models of heavy-quark dynamics and the strong force. Publication is set for Physical Review Letters.