$Λ(1520)$ and $Σ(1385)$ in the nuclear medium

Abstract

Recent studies of the $Λ(1520)$ resonance within chiral unitary theory with coupled channels find the resonance as a dynamically generated state from the interaction of the decuplet of baryons and the octet of mesons, essentially a quasibound state of $πΣ^*(1385)$ in this case, although the coupling of the $Λ(1520)$ to the $\bar{K}N$ and $πΣ$ makes this picture only approximate. The $πΣ^*(1385)$ decay channel of the $Λ(1520)$ is forbidden in free space for the nominal mass of the $Σ^*(1385)$, but the coupling of the $π$ to $ph$ components in the nuclear medium opens new decay channels of the $Λ(1520)$ in the nucleus and produces a much larger width. Together with medium modifications of the $\bar{K}N$ and $πΣ$ decay channels, the final width of the $Λ(1520)$ at nuclear matter density is more than five times bigger than the free one. We perform the calculations by dressing simultaneously the $Λ(1520)$ and the $Σ^*(1385)$ resonances, finding moderate changes in the mass but substantial ones in the width of both resonances.

20 pages, 6 figures; comparison made to data, new references and new (small) decay channel included