Observation of an excited B[± over c] meson state with the ATLAS detector

Abstract

A search for excited states of the B[± over c] meson is performed using 4.9 fb[superscript −1] of 7 TeV and 19.2 fb[superscript −1] of 8 TeV pp collision data collected by the ATLAS experiment at the LHC. A new state is observed through its hadronic transition to the ground state, with the latter detected in the decay B[± over c] → J/ψπ[superscript ±]. The state appears in the m(B[± over c]π[superscript +]π[superscript −]) − m(B[± over c]) − 2m(π[superscript ±]) mass difference distribution with a significance of 5.2 standard deviations. The mass of the observed state is 6842 ± 4 ± 5 MeV, where the first error is statistical and the second is systematic. The mass and decay of this state are consistent with expectations for the second S-wave state of the B[± over c] meson, B[± over c](2S).