Abstract
A search for excited states of the Bc(±) 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 Bc(±)→J/ψπ(±). The state appears in the m(Bc(±)π(+)π(-))-m(Bc(±))-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 Bc(±) meson, Bc(±)(2S).
Highlights
The BÆc meson was first observed by the CDF experiment in the semileptonic decay mode [1], and its hadronic decay mode was observed later by both the CDF [2] and the D0 [3] experiments
This Letter presents the observation of a new state whose mass is consistent with predictions for the BÆc ð2SÞ, the second S-wave state of the BÆc meson
The BÆc ð2SÞ state is reconstructed in the decay to the BÆc meson and two oppositely charged pions, with the BÆc reconstructed through its decay to J=ψπÆ, J=ψ → μþμ−
Summary
The BÆc meson was first observed by the CDF experiment in the semileptonic decay mode [1], and its hadronic decay mode was observed later by both the CDF [2] and the D0 [3] experiments. The second S-wave state, BÆc ð2SÞ, is predicted to have a mass in the range 6835–6917 MeV [5]. The S-wave state, BÆc ð3SÞ, is predicted to have a mass above the threshold for decay into a BD meson pair.
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