QCD S Parameter from Inhomogeneous Bethe-Salpeter Equation
Abstract
We calculate the low-energy parameter S in QCD, which is also known as L_{10}, and the pion decay constant f_\pi using inhomogeneous Bethe-Salpeter equation in improved ladder approximation. To extract these quantities we calculate the ``V-A'' two-point function, \Pi_{VV}(q^2) - \Pi_{AA}(q^2), in space-like region. We obtain S = 0.43 \sim 0.48, which is about 30% larger than the experimental value. The calculated f_\pi is well consistent with the result by solving the homogeneous Bethe-Salpeter equation for pion. We also evaluate parameter in SU(3) gauge theory with N_D doublets of fermions in connection with walking technicolor model, and find that the value of S/N_D hardly depends on N_D.
Cite
@article{arxiv.hep-ph/9406402,
title = {QCD S Parameter from Inhomogeneous Bethe-Salpeter Equation},
author = {Masayasu Harada and Yuhsuke Yoshida},
journal= {arXiv preprint arXiv:hep-ph/9406402},
year = {2014}
}
Comments
22 pages (LaTeX), 6 PostScript figures are included as uuencoded-compressed-tar file at the end (need 'epsf.tex' macro package), KUNS-1270 HE(TH)94/09