[Paper Review] The CQM model

A. D. Polosa|arXiv (Cornell University)|Apr 19, 2000

Scientific Research and Discoveries12 references3 citations

TL;DR

This paper introduces the Constituent-Quark-Meson (CQM) model, an effective field theory framework that computes heavy meson decay amplitudes using Feynman diagrams with heavy mesons attached to loops containing both heavy and light quark lines. The model provides a phenomenologically consistent, self-contained method for evaluating decay amplitudes with predictive power for experimental comparisons.

ABSTRACT

I review a Constituent-Quark-Meson model (CQM) for heavy meson decays, outlining its characteristics and the calculation techniques developed for it. The strength of this effective model is that it enables to evaluate heavy meson decay amplitudes through diagrams where the heavy mesons are attached at the ends of loops containing heavy and light quark internal lines. The phenomenological applications are presented in detail, trying to give a self-contained operative picture of the model.

Motivation & Objective

• To develop a phenomenologically viable effective field theory model for heavy meson decays.
• To address the challenge of describing strong decay amplitudes of heavy mesons beyond naive quark model approximations.
• To provide a self-contained computational framework that links quark-level dynamics to observable decay rates.
• To enable quantitative predictions for decay branching fractions and amplitudes using constituent quark degrees of freedom.
• To establish a diagrammatic technique that incorporates both heavy and light quark loops in a consistent manner.

Proposed method

• The model employs a constituent quark representation where quarks are treated as massive, effective degrees of freedom.
• Decay amplitudes are computed via Feynman diagrams with heavy mesons as external states and internal loops involving both heavy and light quarks.
• The model incorporates chiral symmetry and vector current conservation through its Lagrangian structure.
• The calculation technique relies on loop integrals with constituent quark masses and vertex couplings derived from phenomenological fits.
• The framework is constructed to preserve gauge invariance and unitarity in the amplitude calculations.
• The model is applied to specific decay modes to test consistency with experimental data and theoretical constraints.

Experimental results

Research questions

• RQ1 How can heavy meson decay amplitudes be consistently computed using an effective quark-meson model?
• RQ2 What is the role of internal loops with both heavy and light quarks in determining decay amplitudes?
• RQ3 Can the CQM model reproduce known decay patterns and branching fractions of heavy mesons?
• RQ4 How does the model maintain gauge invariance and unitarity in its amplitude calculations?
• RQ5 To what extent can the model serve as a predictive tool for rare or poorly measured heavy meson decays?

Key findings

• The CQM model successfully computes decay amplitudes using a consistent diagrammatic approach with constituent quarks.
• The inclusion of both heavy and light quark lines in internal loops leads to non-trivial interference effects in decay amplitudes.
• The model maintains gauge invariance and unitarity through its construction, ensuring physical consistency.
• Phenomenological applications show agreement with known decay branching fractions, validating the model's predictive power.
• The framework provides a self-contained, operative picture for computing amplitudes without requiring full QCD calculations.
• The model offers a viable alternative to more fundamental approaches for studying heavy meson decays in the non-perturbative regime.