Oblique S and T Constraints on Electroweak Strongly-Coupled Models with a Light Higgs

Abstract

Using a general effective Lagrangian implementing the chiral symmetry breaking SU(2)L x SU(2)R -> SU(2){L+R}, we present a one-loop calculation of the oblique S and T parameters within electroweak strongly-coupled models with a light scalar. Imposing a proper ultraviolet behaviour, we determine S and T at next-to-leading order in terms of a few resonance parameters. The constraints from the global fit to electroweak precision data force the massive vector and axial-vector states to be heavy, with masses above the TeV scale, and suggest that the W+W- and ZZ couplings of the Higgs-like scalar should be close to the Standard Model value. Our findings are generic, since they only rely on soft requirements on the short-distance properties of the underlying strongly-coupled theory, which are widely satisfied in more specific scenarios.

Comments: 33 pages, 7 figures. Version published in JHEP. Some references and sentences have been added to facilitate the discussion. Specifically, note comments and references about possible fermionic resonances in Section 3. arXiv admin note: text overlap with arXiv:1206.3454