2010/08/31 by Stefano Di Chiara, Claudio Pica, Francesco Sannino · 1 citation
Physics and Astronomy · #hep-ph #hep-ex #hep-lat
paper · pdf · doi:10.1016/j.physletb.2011.05.008
published as Phys.Lett.B700:229-235,2011 · Version to match the one published in Phys. Lett. B. The file is prepared in the 2-columns RevTeX format has 9 pages, 4 figures and one table
arxiv created 2011/05/15 · arxiv updated 2011/06/13
We extend the results of [arXiv:1006.0207 [hep-lat]] by computing the S-parameter at two loops in the perturbative region of the conformal window. Consistently using the expression for the location of the infra-red fixed point at the two-loop order we express the S-parameter in terms of the number of flavors, colors and matter representation. We show that S, normalized to the number of flavors, increases as we decrease the number of flavors. Our findings support the conjecture presented in [arXiv:1006.0207 [hep-lat]] according to which the normalized value of the S-parameter at the upper end of the conformal window constitutes the lower bound across the entire phase diagram for the given underlying asymptotically free gauge theory. We also show that the non-trivial dependence on the number of flavors merges naturally with the non-perturbative estimate of the S-parameter close to the lower end of the conformal window obtained using gauge duality [arXiv:1007.0254 [hep-ph]]. Our results are natural benchmarks for lattice computations of the S-parameter for vector-like gauge theories.