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

TL;DR

This study analyzes the radiative decays of the $ ext{Lambda}(1520)$ resonance using a chiral unitary approach, incorporating new computational techniques, and compares results with experimental data to explore its internal structure.

Contribution

It introduces a gauge-invariant calculation of $ ext{Lambda}(1520)$ radiative decays with meson-baryon interactions, including photon couplings to intermediate baryons for the first time.

Findings

Calculated decay width $ ext{Gamma}( ext{Lambda}(1520) o extgamma extSigma^0)$ matches BESIII data.

Predicted $ ext{Gamma}( ext{Lambda}(1520) o extgamma extLambda)$ is smaller than CLAS results.

Highlights the complex structure of $ ext{Lambda}(1520)$ and the need for refined models.

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, 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.