Radiative decays of the $\Lambda (1520)$ as a dynamically generated resonance

Abstract

Inspired by the latest BESIII measurement of the $\Lambda (1520)\to \gamma {\Sigma }^0$ radiative decay, we systematically study the decays $\Lambda (1520)\to \gamma \Lambda ({\Sigma }^0)$ within the chiral unitary approach, where the $\Lambda (1520)$ is treated as a dynamically generated resonance from meson-baryon interactions. Compared with previous chiral unitary studies, we adopt dimensional regularization for $S$-wave loop integrals to preserve gauge invariance and, for the first time, include Feynman diagrams with photon coupling to intermediate baryons. Our calculated partial decay width $\Gamma (\Lambda (1520)\to \gamma {\Sigma }^0)$ agrees well with the new BESIII data, whereas the predicted $\Gamma (\Lambda (1520)\to \gamma \Lambda )$ is considerably smaller than the CLAS experimental result. By comparing our results with predictions from various quark models, together with an analysis of the $\Lambda (1520)$ compositeness, we discuss the internal nature of the $\Lambda (1520)$ resonance, highlight its complex component structure, and stress the need for more refined theoretical frameworks and further experimental measurements.

9 pages,6 figures,3 tables; Matches the published version