Study of nucleon and $\Delta$ resonances from a systematic analysis of $K^\ast\Sigma$ photoproduction

Abstract

A systematic analysis of the $K^\ast\Sigma$ photoproduction off proton is performed with all the available differential cross section data. We carry out a strategy different from the previous studies of these reactions, where, instead of fixing the parameters of the added resonances from PDG or pentaquark models, we add the resonance with a specific $J^P$ and leave its parameters to be determined from the experimental data. When adding only one resonance, the best result is to add one $N(3/2^-)$ resonance around $2097$ MeV, which substantially reduces the $\chi^2$ per degree of freedom to $1.35$. There are two best solutions when adding two resonances, one is to add one $N^\ast(3/2^-)$ and one $N^\ast(7/2^-)$, the other is to add one $N^\ast(3/2^-)$ and one $\Delta^\ast(7/2^-)$, leading the $\chi^2$ per degree of freedom to be $1.10$ and $1.09$, respectively. The mass values of the $N^\ast(3/2^-)$ in the two resonance solutions are both near $2070$ MeV. Our solutions indicate that the $N(3/2^-)$ resonance around $2080$ MeV is strongly coupled with the $K^\ast\Sigma$ final state and support the molecular picture of $N(2080, 3/2^-)$.