QCD Sum Rules and the Induced Pseudoscalar Coupling

TL;DR

This paper extends QCD sum rule methods to determine the induced pseudoscalar coupling constant g_P, providing a stable prediction that tests the PCAC hypothesis and discusses future prospects of the approach.

Contribution

It introduces a new QCD sum rule for g_P that isolates higher-order effects and demonstrates its stability, advancing the application of sum rules in hadronic physics.

Findings

Stable prediction for g_P obtained

Validates the PCAC hypothesis

Discusses future of QCD sum rule methods

Abstract

We present an extension of the QCD sum rule method in the external fields so as to determine the induced pseudoscalar coupling constant g_P, which tests the validity of the partially conserved axial current (PCAC) hypothesis. This is essentially that we pick out the "higher-order" effects of both the hadron and quark (QCD) sides. A specific QCD sum rules for g_P is obtained and its prediction is briefly analyzed. It turns out that the final prediction on g_P is extremely stable. In view of the versatile nature of the present QCD sum rule methods, we appendix some discussions on the possible future of the method.