Role of five-quark components in radiative and strong decays of the Lambda(1405) resonance

Abstract

Within an extended chiral constituent quark model, three- and five-quark structure of the $S_{01}$ resonance $\Lambda (1405)$ is investigated. Helicity amplitudes for the electromagnetic decays ($\Lambda (1405)\to \Lambda (1116)\gamma$, $\Sigma (1194)\gamma$), and transition amplitudes for strong decays ($\Lambda (1405)\to \Sigma (1194)\pi$, $K^{-}p$) are drived, as well as the relevant decay widths. The experimental value for the strong decay width, ${\Gamma }_{\Lambda (1405)\to (\Sigma \pi {)}^{\circ }}=50\pm 2$ MeV, is well reproduced with about 50% of five-quark admixture in the $\Lambda (1405)$. Important effects due to the configuration mixings among ${\Lambda }_1^2{P}_A$, ${\Lambda }_8^2{P}_M$ and ${\Lambda }_8^4{P}_M$ are found. In addition, transitions between the three- and five-quark components in the baryons turn out to be significant in both radiative and strong decays of the $\Lambda (1405)$ resonance.

Comments: typos and numerical mistakes corrected, to appear in Phys. Rev. C