Observation of an Excited B_{c}^{±} Meson State with the ATLAS Detector.

Aad, G ; Abbott, B ; Abdallah, J ; Abdel Khalek, S ; Abdinov, O ; Aben, R ; Abi, B ; Abolins, M ; AbouZeid, O S and Abramowicz, H , et al. (2014) In Physical Review Letters 113(21).
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_{c}^{±}π^{+}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).
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