Suppression of decay widths in singly heavy baryons induced by the $U_A(1)$ anomaly

Abstract

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 ${\Lambda }_Q(1/2^{-})$.

Comments: 9 pages, 6 figures