A search for excited states of the B±c meson is performed using 4.9 fb−¹ of 7 TeV and 19.2 fb−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±c→J/ψπ±. The state appears in the m(B±cπ+π−)−m(B±c)−2m(π±) 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±c meson, B±c(2S).
Aad, G., Abbott, B., Abdallah, J., Abdel Khalek, S., Abdinov, O., Aben, R., et al. (2014). Observation of an Excited B-c(+/-) Meson State with the ATLAS Detector. PHYSICAL REVIEW LETTERS, 113(21), 1-18 [10.1103/PhysRevLett.113.212004].