QCD Sum Rules and 1/$N_c$ expansion

TL;DR

This paper uses 1/Nc expansion and QCD sum rules to classify hadronic states, distinguish different contributions, and analyze the mass behavior of 4-quark systems, providing insights into nontrivial correlations.

Contribution

It introduces a method combining 1/Nc expansion with QCD sum rules to differentiate hadronic state contributions and analyze 4-quark system masses.

Findings

Separation of instanton, glueball, and ππ scattering states by 1/Nc.

Identification of nontrivial mass reduction correlations in 4-quark systems.

Analysis of bare resonance poles without mixing effects.

Abstract

The 1/$N_c$ arguments are developed to classify the hadronic states in the correlators. Arguments applied to the $\sigma$ meson correlator enable to separate the instanton, glueball, and, in particular, the $\pi\pi$ scattering states by $1/N_c$ from both 2q and 4q correlators. The bare resonance pole with no mixing effects are analyzed with the QCD sum rules (QSR). The results suggest the existence of nontrivial correlation for the mass reduction of 4q system.