Negative parity $Λ$ and $Σ$ resonances coupled to pseudoscalar and vector mesons

K. P. Khemchandani, A. Martínez Torres, H. Nagahiro, A. Hosaka

Published 2012-03-30Version 1

An exploration of the dynamically generated $\Lambda$ and $\Sigma$ resonances has been made in the vector meson-baryon (VB) systems coupled to pseudoscalar meson-baryon (PB) channels. The VB interactions are obtained from the Lagrangians written within the hidden local symmetry which, in addition to Yukawa-type vector-baryon-baryon (VBB) vertices, naturally gives rise to a contact interaction. Using the VBB vertices, we calculate the $t$-, $s$- and $u$-channel diagrams considering the octet baryon exchange in the latter two cases. For the PB channels we rely on the the Weingberg-Tomozawa interactions and calculate the PB $\leftrightarrow$ VB transition amplitudes extending the Kroll-Ruderman theorem by replacing the photon by the vector mesons. In addition to the low-lying $\Lambda(1405)$, $\Lambda(1670)$ found in previous works, we find resonances which coincide well with: $\Lambda(2000)$, $\Sigma(1750) S_{11}$, $\Sigma(1940) D_{13}$, $\Sigma(2000) S_{11}$ and predict three $\Lambda^*$'s with $J^\pi = 3/2^-$ and masses: $1754 - i2$ MeV, $1862 - i33$ MeV, $2139 - i14$ MeV together with a broad $1/2^-$ $\Sigma^*$ with mass $\sim$ 1430 MeV. We find that most of these next-to-low-lying states couple weakly with the pseudoscalar mesons, which implies that it is important to study the reactions with VB final states in order to obtain a reliable information on the properties of such resonances.