Observation of a new $\hat{I}{ž}_b^{-}$ resonance

Abstract

From samples of $pp$ collision data collected by the LHCb experiment at $\sqrt{s}=7$, $8$ and $13$ TeV corresponding to integrated luminosities of 1.0, 2.0 and 1.5 fb${}^{-1}$, respectively, a peak in both the $\hat{I}{›}_b^0{K}^{-}$ and $\hat{I}{ž}_b^0\ddot{I}{€}^{-}$ invariant mass spectra is observed. In the quark model, radially and orbitally excited $\hat{I}{ž}_b^{-}$ resonances with quark content $bds$ are expected. Referring to this peak as $\hat{I}{ž}_b(6227{)}^{-}$, the mass and natural width are measured to be $m_{\hat{I}{ž}_b(6227{)}^{-}}=6226.9\pm 2.0\pm 0.3\pm 0.2$ MeV/$c^2$ and $\hat{I}{“}_{\hat{I}{ž}_b(6227{)}^{-}}=18.1\pm 5.4\pm 1.8$ MeV/$c^2$, where the first uncertainty is statistical, the second is systematic, and the third, on $m_{\hat{I}{ž}_b(6227{)}^{-}}$, is due to the knowledge of the $\hat{I}{›}_b^0$ baryon mass. Relative production rates of the $\hat{I}{ž}_b(6227{)}^{-}\to \hat{I}{›}_b^0{K}^{-}$ and $\hat{I}{ž}_b(6227{)}^{-}\to \hat{I}{ž}_b^0\ddot{I}{€}^{-}$ decays are also reported.

8 pages, 3 figures, All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2018-013.html