S parameter in QCD from domain wall fermions

Abstract

We have computed the SU(2) low-energy constant l₅ and the mass splitting between charged and neutral pions from a lattice QCD simulation of n(sub)f=2+1 flavors of domain wall fermions at a scale of a⁻¹=2.33 GeV. Relating l₅ to the S parameter in QCD we obtain a value of S(m(sub)H=120 GeV)=0.42(7), in agreement with previous determinations. Our result can be compared with the value of S from electroweak precision data which constrains strongly interacting models of new physics like technicolor. This work in QCD serves as a test for the methods to compute the S parameter with domain wall fermions in theories beyond the standard model. We also infer a value for the pion mass splitting in agreement with experiment.