EPJ

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EPJ A - Hadrons and Nuclei
Hadrons and Nuclei
Eur. Phys. J. A 7, 121-125

$\pi NN$ coupling determined beyond the chiral limit

Hungchong Kim

Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan

Received: 8 July 1999 / Revised version: 20 August 1999 Communicated by W. Weise

Abstract
Within the conventional QCD sum rules, we calculate the $\pi NN$coupling constant, $g_{\pi N}$, beyond the chiral limit using two-point correlation function with a pion. For this purpose, we consider the Dirac structure, $i\gamma_5$, at $m_\pi^2$ order in the expansion of the correlator in terms of the pion momentum. For a consistent treatment of the sum rule, we include the linear terms in quark mass as they constitute the same chiral order as $m_\pi^2$. In this sum rule, we obtain $g_{\pi N}=13.3\pm 1.2$, which is very close to the empirical $\pi NN$ coupling. This demonstrates that going beyond the chiral limit is crucial in determining the coupling.

PACS
13.75.Gx Pion-baryon interactions - 12.38.Lg Other nonperturbative calculations - 11.55.Hx Sum rules

Copyright Società Italiana di Fisica, Springer-Verlag 2000

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