Observation of an Excited B_c ^{±} Meson State with the ATLAS Detector



A search for excited states of theB(±)(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⁻) − mB(±)(c) 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).



B mesons, Unbinned maximum likelihood, Proton-proton interactions



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