Mixings of 4-quark components in light non-singlet scalar mesons in QCD sum rules

TL;DR

This paper investigates the mixing of 4-quark and 2-quark components in light non-singlet scalar mesons using QCD sum rules, revealing that 4-quark states dominate the lowest mass states.

Contribution

It introduces a new formulation to evaluate cross correlators of different Fock states in QCD sum rules, specifically applied to scalar mesons.

Findings

4-quark operators predict lower masses than qar q operators

4-quark states constitute about 70-90% of the lowest mass states

The method effectively evaluates Fock state mixings in mesons

Abstract

Mixings of 4-quark components in the non-singlet scalar mesons are studied in the QCD sum rules. We propose a formulation to evaluate the cross correlators of q\bar q and qq\bar q \bar q operators and to define the mixings of different Fock states in the sum rule. It is applied to the non-singlet scalar mesons, a_0 and K_0^\ast. It is found that the 4-quark operators predict lower masses than the q\bar q operators and that the 4-quark states occupy about 70-90% of the lowest mass states.