Structure of the $Ξ_b(6227)^-$ Resonance

Abstract

We explore the recently observed $Ξ_b(6227)^{-}$ resonance to fix its quantum numbers. To this end, we consider various possible scenarios: It can be considered as either 1P/2S excitations of the $Ξ_b^-$ and $Ξ_b'(5935)^{-}$ ground state baryons with spin-$\frac{1}{2}$ or 1P/2S excitations of the ground state $Ξ_b(5955)^{-}$ with spin-$\frac{3}{2}$. We calculate the masses of the possible angular-orbital $1P$ and $2S$ excited states corresponding to each channel employing the QCD sum rule technique. It is seen that all the obtained masses are in agreement with the experimentally observed value, implying that the mass calculations are not enough to distinguish the quantum numbers of the state under question. Therefore, we extend the analysis to investigate the possible decays of the same excited states into $Λ_b^0 K^-$ and $Ξ_b^-π$. Using the light cone QCD sum rule method, we calculate the corresponding strong coupling constants, which are used to extract the decay widths of the modes under consideration. Our results on decay widths indicate that the $Ξ_b(6227)^{-}$ is $1P$ angular-orbital excited state of the $Ξ_b(5955)^{-}$ baryon with quantum numbers $J^P=\frac{3}{2}^{-}$.