[Paper Review] Remarks on the hidden color components in multi-quark study

Fan Wang, Jialun Ping+1 more|arXiv (Cornell University)|Nov 4, 2017

History of Science and Medicine1 references3 citations

TL;DR

This paper investigates the physical role of hidden color components in multi-quark systems, arguing they are not merely mathematical artifacts but physically meaningful degrees of freedom due to the failure of quark-only descriptions to account for SU(3) color gauge invariance. It demonstrates that hidden color components cannot be fully replaced by colorless hadronic states when gauge links and dynamical gluon effects are included, especially in compact systems or hybrids, where they contribute to short-range repulsion and exotic hadron structure.

ABSTRACT

Problems related to the application of hidden color components in multi-quark systems are discussed in this report.

Motivation & Objective

• To clarify the physical significance of hidden color components in multi-quark systems beyond mathematical recoupling.
• To challenge the view that hidden color components are spurious by showing their necessity in maintaining SU(3) color gauge invariance.
• To argue that in compact or hybrid systems, hidden color components cannot be replaced by colorless hadronic states due to missing gauge links.
• To highlight the role of hidden color in short-range repulsion and exotic hadron spectroscopy, especially in systems like d* dibaryon.

Proposed method

• Uses group theory to analyze the transformation between symmetry bases (group chain classified) and physical bases (cluster states) in SU(4) and SU(6) quark models.
• Applies SU^c(3) × SU^fσ(6) group chains to describe color and flavor-spin symmetries in six-quark and penta-quark systems.
• Considers the role of gauge links in ensuring local color gauge invariance, which is missing in standard quark cluster models.
• Analyzes the implications of lattice QCD string structures and color string models, where different color string strengths break the equivalence between hidden color and colorless components.
• Compares cluster model approximations with full many-body treatments, showing limitations in compact systems.
• Evaluates the physical effects of hidden color components in NN interactions, d* dibaryon width, and color van der Waals forces.

Experimental results

Research questions

• RQ1 Can hidden color components in multi-quark systems be fully replaced by colorless hadronic states through quark rearrangement?
• RQ2 What is the physical role of hidden color components when SU(3) color gauge invariance is properly enforced via gauge links?
• RQ3 Why do hidden color components remain physically relevant in compact multi-quark systems like d* despite quark rearrangement?
• RQ4 How do dynamical gluon effects and color string structures affect the physical reality of hidden color components?
• RQ5 To what extent do hidden color components contribute to short-range repulsion in NN scattering and exotic hadron widths?

Key findings

• Hidden color components are not merely mathematical constructs; they are physically meaningful when the full SU(3) color gauge invariance, including gauge links, is enforced.
• The standard quark cluster model fails to account for gauge invariance, making the replacement of hidden color by colorless components invalid in dynamical systems.
• In compact systems like the d* dibaryon, the cluster approximation breaks down, and hidden color components must be treated as independent physical degrees of freedom.
• Lattice QCD results confirm that linear or quadratic confinement potentials are screened by q̄q excitation, implying that hidden color effects are dynamically relevant.
• The color string model, which incorporates different string strengths, shows that hidden color components cannot be eliminated by recoupling, confirming their physical reality.
• Physical effects such as short-range repulsion in NN scattering and small widths of exotic states like d* are not primarily due to hidden color components, but their presence is still essential for gauge invariance and correct dynamics.