Diquarks: a QCD sum rule perspective

TL;DR

This paper develops a QCD sum rule approach incorporating explicit diquark fields to analyze the internal structure of Lambda baryons, suggesting they can be modeled as diquark-quark systems and identifying a diquark mass parameter.

Contribution

It introduces a phenomenological QCD sum rule with an explicit diquark field, providing new insights into the diquark-quark structure of Lambda baryons and the duality relation among model parameters.

Findings

Sum rule effectively describes Lambda, Lambda_c, and Lambda_b baryons.

Identifies a diquark mass of approximately 0.4 GeV as a constituent diquark mass.

Establishes a duality relation among diquark parameters.

Abstract

We propose a phenomenological QCD sum rule with an explicit diquark field to investigate the essential ingredients inside the hadrons. Introducing the mass (m_\phi) and the condensate (\phi^2) for the diquark field as parameters in the model, we find that the sum rule works well for Lambda, Lambda_c and Lambda_b. This implies that these Lambda baryons can be represented by a diquark and a quark configuration. We also find that there is a duality relation among the parameters (m_\phi, \phi^2), for which the sum rule is equally good. In the limit when \phi^2 =0 we find m_\phi=0.4 GeV, which can be thought as the constituent diquark mass.