S parameter and parity doubling below the conformal window

Abstract

Recently the Lattice Strong Dynamics Collaboration reported a reduction of the electroweak S parameter for SU(3) gauge theory with Nf = 6 fermions in the fundamental representation, compared to scaled-up QCD. Here I provide additional details of our calculation. I discuss our use of conserved lattice currents; the relation to vector–axial parity doubling; finite-volume effects; and the sensitivity of our results to the number of fermion doublets with chiral electroweak couplings. Results presented here include additional data, and do not affect our previously-published conclusions.