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

TL;DR

This paper investigates how the $U_A(1)$ anomaly influences decay widths of excited singly heavy baryons, revealing suppression effects and modifications to decay relations using an effective chiral Lagrangian with a diquark model.

Contribution

It introduces a novel analysis of the $U_A(1)$ anomaly impact on heavy baryon decays within a diquark-based effective chiral Lagrangian framework, highlighting decay suppression mechanisms.

Findings

The $U_A(1)$ anomaly causes inverse mass ordering between strange and non-strange SHBs.

The anomaly modifies the Goldberger-Treiman relation and suppresses certain decay widths.

Decay widths of $ ext{Lambda}_Q(1/2^-) o ext{Lambda}_Q(1/2^+) ext{eta}$ are significantly reduced.

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 $\Lambda_Q (1/2^-)$.