6533b839fe1ef96bd12a5a08

RESEARCH PRODUCT

Theoretical description of the decays Λb→Λ(*)(12±,32±)+J/ψ

subject

description

We calculate the invariant and helicity amplitudes for the transitions ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}^{(*)}({J}^{P})+J/\ensuremath{\psi}$, where the ${\mathrm{\ensuremath{\Lambda}}}^{(*)}({J}^{P})$ are $\mathrm{\ensuremath{\Lambda}}(sud)$-type ground and excited states with ${J}^{P}$ quantum numbers ${J}^{P}={\frac{1}{2}}^{\ifmmode\pm\else\textpm\fi{}}$, ${\frac{3}{2}}^{\ifmmode\pm\else\textpm\fi{}}$. The calculations are performed in the framework of a covariant confined quark model previously developed by us. We find that the values of the helicity amplitudes for the ${\mathrm{\ensuremath{\Lambda}}}^{*}(1520,{\frac{3}{2}}^{\ensuremath{-}})$ and the ${\mathrm{\ensuremath{\Lambda}}}^{*}(1890,{\frac{3}{2}}^{+})$ are suppressed compared with those for the ground state $\mathrm{\ensuremath{\Lambda}}(1116,{\frac{1}{2}}^{+})$ and the excited state ${\mathrm{\ensuremath{\Lambda}}}^{*}(1405,{\frac{1}{2}}^{\ensuremath{-}})$. This analysis is important for the identification of the hidden charm pentaquark states ${P}_{c}^{+}(4380)$ and ${P}_{c}^{+}(4450)$ which were discovered in the decay chain ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}{P}_{c}^{+}(\ensuremath{\rightarrow}pJ/\ensuremath{\psi})+{K}^{\ensuremath{-}}$ because the cascade decay chain ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}^{*}({\frac{3}{2}}^{\ifmmode\pm\else\textpm\fi{}})(\ensuremath{\rightarrow}p{K}^{\ensuremath{-}})+J/\ensuremath{\psi}$ involves the same final state.