Enhanced non-quark-antiquark and non-glueball Nc behavior of light scalar mesons

TL;DR

The paper demonstrates that precise dispersive data analyses challenge the quark-antiquark and glueball interpretations of light scalar mesons, revealing unnatural 1/Nc behavior inconsistent with standard large-Nc QCD expectations.

Contribution

It introduces a method using scattering observables with suppressed 1/Nc corrections to analyze the nature of light scalar mesons, questioning their quark-antiquark or glueball classification.

Findings

Light scalar mesons show unnatural 1/Nc behavior.

Standard 1/Nc scaling does not fit scalar mesons.

Dispersive data analysis challenges traditional interpretations.

Abstract

We show that the latest and very precise dispersive data analyses require a large and very unnat- ural fine-tuning of the 1/Nc expansion at Nc = 3 if the f_0(600) and K(800) light scalar mesons are to be considered predominantly quark-antiquark states, which is not needed for light vector mesons. For this, we use scattering observables whose 1/Nc corrections are suppressed further than one power of 1/Nc for quark-antiquark or glueball states, thus enhancing contributions of other nature. This is achieved without using unitarized ChPT, but if it is used we can also show that it is not just that the coefficients of the 1/Nc expansion are unnatural, but that the expansion itself does not even follow the expected 1/Nc scaling of a glueball or a quark-antiquark meson.