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