  We study strong and radiative decays of excited singly heavy baryons (SHBs)
using an effective chiral Lagrangian based on the diquark picture proposed in
Ref. [1]. The effective Lagrangian contains a $U_A (1)$ anomaly term, which
induces an inverse mass ordering between strange and non-strange SHBs with
spin-parity $1/2^-$. We find that the effect of the $U_A (1)$ anomaly combined
with flavor-symmetry breaking modifies the Goldberger-Treiman relation for the
mass difference between the ground state $\Lambda_Q (1/2^+)$ and its chiral
partner $\Lambda_Q (1/2^-)$, and $\Lambda_Q (1/2^-) \Lambda_Q (1/2^+) \eta$
coupling, which results in suppression of the decay width of $\Lambda_Q (1/2^-)
\to \Lambda_Q (1/2^+) \eta$. We also investigate the other various decays such
as $\Lambda_Q (1/2^-) \to \Sigma_Q (1/2^+, \, 3/2^+) \pi \pi$, $\Lambda_Q
(1/2^-) \to \Sigma_Q (1/2^+) \pi$, $\Lambda_Q (1/2^-) \to \Sigma_Q (1/2^+, \,
3/2^+) \gamma$, and $\Lambda_Q (1/2^-) \to \Lambda_Q (1/2^+) \pi^0$ for wide
range of mass of $\Lambda_Q (1/2^-)$.
