Mechanism for a next-to-lowest lying scalar meson nonet

TL;DR

This paper proposes a mixing mechanism between a conventional p-wave scalar quark-antiquark nonet and a lighter four-quark scalar nonet to explain the properties of certain scalar mesons, resolving existing puzzles.

Contribution

It introduces a natural mixing model between two scalar nonets, explaining the observed meson spectrum and properties more coherently than previous models.

Findings

The mixing explains the mass hierarchy of scalar mesons.

It accounts for the properties of a0(980), a0(1450), and K0*(1430).

The model resolves puzzles in the conventional quark model interpretation.

Abstract

Recent work suggests the existence of a non-conventional lowest-lying scalar nonet containing the a0(980). Then the a0(1450) and also the K0*(1430) are likely candidates to belong to a conventional p-wave $q \bar q$ nonet. However a comparison of their properties with those expected on this basis reveals a number of puzzling features. It is pointed out that these puzzles can be resolved in a natural and robust way by assuming a ``bare'' conventional p-wave scalar $q \bar q$ nonet to mix with a lighter four quark $qq \bar q \bar q$ scalar nonet to form new ``physical'' states. The essential mechanism is driven by the fact that the isospinor is lighter than the isovector in the unmixed $qq \bar q \bar q$ multiplet.