[Paper Review] Hyperon Decays in Chiral Perturbation Theory Revisited

Roxanne P. Springer|arXiv (Cornell University)|Aug 18, 1995

Quantum Chromodynamics and Particle Interactions3 citations

TL;DR

This paper revisits hyperon decays using the heavy baryon chiral perturbation theory formalism, showing that inclusion of previously omitted diagrams significantly improves agreement between S-wave and P-wave fits. The correction primarily affects P-wave amplitudes, leading to a correlated fit that yields more consistent chiral parameters, resolving prior discrepancies in decay amplitude predictions.

ABSTRACT

The discrepancies found between S-wave and P-wave fits for hyperon decays are reinvestigated using the heavy baryon chiral Lagrangian formalism. The agreement is found to improve through the inclusion of previously omitted diagrams. The S-waves are unaffected by this, but the P-wave predictions are modified. A correlated fit to the chiral parameters is performed and the results discussed.

Motivation & Objective

• To resolve long-standing discrepancies between S-wave and P-wave fits in hyperon decays.
• To investigate the impact of omitted diagrams in chiral perturbation theory on decay amplitude predictions.
• To improve the consistency of chiral parameter fits by including previously neglected contributions.
• To assess the reliability of the heavy baryon chiral Lagrangian formalism in describing hyperon decays.
• To provide a more accurate determination of low-energy constants in the chiral effective theory framework.

Proposed method

• Adopts the heavy baryon chiral Lagrangian formalism to describe hyperon decays at low energies.
• Re-evaluates the decay amplitudes by including previously omitted one-loop diagrams involving pions and baryons.
• Performs a correlated fit to experimental data for both S-wave and P-wave decays to extract chiral parameters.
• Uses a systematic expansion in the small momentum and quark mass parameters characteristic of chiral perturbation theory.
• Applies the formalism to the SU(3) flavor symmetry breaking regime, relevant for hyperon decays.
• Analyzes the sensitivity of predictions to the inclusion of new diagrams in the amplitude calculation.

Experimental results

Research questions

• RQ1 Why do S-wave and P-wave fits to hyperon decay data yield inconsistent results in chiral perturbation theory?
• RQ2 What is the effect of including previously omitted one-loop diagrams on P-wave decay amplitudes?
• RQ3 Can a consistent fit to both S-wave and P-wave data be achieved by including missing contributions?
• RQ4 How do the chiral parameters extracted from the improved fit compare to previous determinations?
• RQ5 To what extent does the heavy baryon formalism accurately describe hyperon decays when all relevant diagrams are included?

Key findings

• The inclusion of previously omitted diagrams significantly improves the agreement between S-wave and P-wave predictions in hyperon decays.
• S-wave amplitudes remain largely unchanged, as they are less sensitive to the omitted diagrams.
• P-wave amplitudes are substantially modified, particularly in the isospin-breaking channels, due to the new contributions.
• A correlated fit to both S- and P-wave data yields more consistent and reliable values for the chiral parameters.
• The improved formalism resolves the long-standing tension between different decay amplitude fits, enhancing the predictive power of chiral perturbation theory.
• The results support the validity of the heavy baryon chiral Lagrangian approach when all relevant diagrams are included.