University of Birmingham Observation of a New b- Resonance

From samples of pp collision data collected by the LHCb experiment at ffiffiffi s p ¼ 7 , 8 and 13 TeV, corresponding to integrated luminosities of 1.0, 2.0 and 1 . 5 fb − 1 , respectively, a peak in both the Λ 0 b K − and Ξ 0 b π − invariant mass spectra is observed. In the quark model, radially andorbitally excited Ξ − b resonanceswith quark content bds are expected. Referringto thispeak as Ξ b ð 6227 Þ − , the mass andnatural width are measured to be m Ξ b ð 6227 Þ − ¼ 6226 . 9 (cid:2) 2 . 0 (cid:2) 0 . 3 (cid:2) 0 . 2 MeV =c 2 and Γ Ξ b ð 6227 Þ − ¼ 18 . 1 (cid:2) 5 . 4 (cid:2) 1 . 8 MeV =c 2 , where the first uncertainty is statistical, the second is systematic, and the third, on m Ξ b ð 6227 Þ − , is due to the knowledge of the Λ 0 b baryon mass. Relative production rates of the Ξ b ð 6227 Þ − → Λ 0 b K − and Ξ b ð 6227 Þ − → Ξ 0 b π − decays are also reported.