$N^*$'s and $Δ$'s generated in vector, pseudoscalar meson-baryon systems

We have recently studied coupled channel interactions of vector and pseudoscalar mesons with octet baryons having total strangeness null and spin-parity $1/2^-$. We, thus, considered $πN$, $ηN$, $K Λ$, $K Σ$, $ρN$, $ωN$, $ϕN$, $K^* Λ$, and $K^*Σ$ with total isospin 1/2 and 3/2. The interactions between pseudoscalar mesons and baryons are obtained by using the Weinberg-Tomozawa theorem. For the case of vector mesons, we calculate $s$-, $t$-, $u$-exchange diagrams and a contact term. The subtraction constants, required to calculate the loop-function in the scattering equations, are constrained by fitting the available experimental data on some of the reactions with pseudoscalar meson-baryon final states. We end up finding resonances which can be related to $N^*(1535)$, $N^*(1650)$ (with a double pole structure), $N^*(1895)$ and $Δ(1620)$. We conclude that these resonances can be, at least partly, interpreted as dynamically generated resonances and that the vector mesons play an important role in determining the dynamical origin of the low-lying $N^*$ and $Δ$ states.

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