The Nucleon Sigma Term from Threshold Parameters

Abstract

A new sum rule determines the nucleon sigma term by the \pi N elastic scattering threshold parameters alone. This "threshold" value of \sigma(2\mu^2) provides an independent check of existing values obtained from global dispersive analyses, and also provides a realistic error assignment. Employing a recent analysis of low energy (T_\pi < 100 MeV) \pi N data our sum rule implies \sigma(2\mu^2) = 71\pm 9 MeV.

Comments: Additional explanations and references, changes in notation, small numerical changes. 11 pages, Revtex, uses epsf.sty, 1 postscript figure. Version to be published in Physics Letters B