Radiative decays of excited Lambda Q baryons in the bound state picture.

Abstract

It is shown that, in the bound state picture, the ${\ensuremath{\Lambda}}_{c}(2593)\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}\ensuremath{\gamma}$ and ${\ensuremath{\Lambda}}_{c}(2625)\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}\ensuremath{\gamma}$ decays are severely suppressed. On the other hand, for their bottom counterparts, which are predicted to have masses of 5900 and 5926 MeV, respectively, they may have significant radiative branching ratios. The ${\ensuremath{\Lambda}}_{b}(5926)\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{b}\ensuremath{\gamma}$ mode possibly dominates over the strong decay mode, while the ${\ensuremath{\Lambda}}_{b}(5900)$ resonance lies below the strong decay threshold and can only decay radiatively. The isospin allowed ${\ensuremath{\Lambda}}_{Q}^{**}\ensuremath{\rightarrow}{\ensuremath{\Sigma}}_{Q}\ensuremath{\gamma}$ mode is expected to be small.