Consistency of coupled-channel effects between off-shell and on-shell chiral models

Determine whether the coupled-channel effects in the S = −1 meson–baryon system behave consistently when computed using fully off-shell covariant unitarized chiral effective field theory up to next-to-leading order versus when computed using the on-shell approximation, particularly in the context of femtoscopic correlation functions for K−p and related coupled channels.

Background

The paper develops a fully off-shell covariant unitarized chiral effective field theory (UχEFT) for S = −1 meson–baryon scattering up to next-to-leading order and compares it to the widely used on-shell approximation. While many scattering observables and correlation functions are similar across schemes, notable differences appear near threshold at NLO.

In analyzing K−p femtoscopic correlation functions, the authors find that the near-threshold discrepancy between off-shell and on-shell results stems from different fitted scattering lengths rather than explicit off-shell effects. However, they note that the consistency of coupled-channel effects across these two dynamical frameworks has not been established, leaving an open question relevant to interpreting femtoscopy data and constraining coupled-channel dynamics.