Cross-channel constraints on resonant antikaon-nucleon scattering

TL;DR

This study demonstrates that covariant baryon chiral perturbation theory, when unitarized, effectively describes meson-baryon scattering data, including the complex structure of the $ar{K}N$ system and the $ ext{Lambda}(1405)$ resonance, up to one-loop order.

Contribution

First global one-loop order analysis of meson-baryon scattering using covariant baryon chiral perturbation theory with unitarization, confirming the two-pole structure of $ ext{Lambda}(1405)$.

Findings

Accurately describes meson-baryon scattering data.

Reduces uncertainties in $ar{K}N$ related quantities.

Supports the two-pole nature of $ ext{Lambda}(1405)$.

Abstract

Chiral perturbation theory and its unitarized versions have played an important role in our understanding of the low-energy strong interaction. Yet, so far, such studies typically deal exclusively with perturbative or nonperturbative channels. In this letter, we report on the first global study of meson-baryon scattering up to one-loop order. It is shown that covariant baryon chiral perturbation theory, including its unitarization for the negative strangeness sector, can describe meson-baryon scattering data remarkably well. This provides a highly non-trivial check on the validity of this important low-energy effective field theory of QCD. We show that the $\bar{K}N$ related quantities can be better described in comparison with those of lower-order studies, and with reduced uncertainties due to the stringent constraints from the $\pi N$ and $K N$ phase shifts. In particular, we find that the two-pole structure of $\Lambda(1405)$ persists up to one-loop order reinforcing the existence of two-pole structures in dynamically generated states.