Two-Point Functions and S-Parameter in QCD-like Theories

TL;DR

This paper computes two-point functions and the S-parameter at two-loop level in low-energy effective theories for various QCD-like models with different fermion representations, providing insights into their low-energy dynamics.

Contribution

It presents the first detailed two-loop calculations of two-point functions and the S-parameter for multiple QCD-like theories with different symmetry breaking patterns.

Findings

Calculated vector, axial-vector, scalar, pseudo-scalar two-point functions up to two loops.

Estimated the S parameter for different QCD-like theories.

Determined the pseudo-scalar decay constant G_M.

Abstract

We calculated the vector, axial-vector, scalar and pseudo-scalar two-point functions up to two-loop level in the low-energy effective field theory for three different QCD-like theories. In addition we also calculated the pseudo-scalar decay constant $G_M$. The QCD-like theories we used are those with fermions in a complex, real or pseudo-real representation with in general n flavours. These case correspond to global symmetry breaking pattern of $SU(n)_L\times SU(n)_R\to SU(n)_V$, $SU(2n)\to SO(2n)$ or $SU(2n)\to Sp(2n)$. We also estimated the S parameter for those different theories.