Revisit to Low Mass Scalar Mesons via Unitarized Chiral Perturbation Theory

TL;DR

This paper investigates the nature of low-mass scalar mesons below 1 GeV using unitarized chiral perturbation theory, revealing different generation mechanisms for f0(980), a0(980), sigma(500), and kappa(900).

Contribution

It applies the multichannel inverse amplitude method to chiral perturbation theory to clarify the origins of scalar mesons below 1 GeV, challenging traditional resonance interpretations.

Findings

f0(980) is a bound state resonance below K-Kbar threshold

a0(980) appears as a cusp at K-Kbar threshold due to channel coupling

sigma(500) and kappa(900) are not conventional resonances

Abstract

We study how the scalar mesons below 1 GeV are generated through the Oller-Oset-Pelaez version of the multichannel inverse amplitude method applied to the chiral perturbation theory. We find out that the f0(980) state is certainly generated as a bound state resonance below the K-Kbar threshold, while the a0(980) state, generated through the channel coupling between the pi-eta and K-Kbar channels, appears as a cusp at the K-Kbar threshold. The so-called sigma(500) and kappa(900) need not be interpreted as the conventional resonances.