One-loop calculation of the oblique S parameter in higgsless electroweak models
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# One-loop calculation of the oblique S parameter in higgsless electroweak models

 dc.contributor.author Pich Zardoya, Antonio dc.contributor.author Rosell Escribà, Ignasi dc.contributor.author Sanz Cillero, Juan José dc.date.accessioned 2015-02-26T12:52:33Z dc.date.available 2015-02-26T12:52:33Z dc.date.issued 2012 dc.identifier.uri http://hdl.handle.net/10550/42411 dc.description.abstract We present a one-loop calculation of the oblique S parameter within Higgsless models of electroweak symmetry breaking and analyze the phenomenological implications of the available electroweak precision data. We use the most general effective Lagrangian with at most two derivatives, implementing the chiral symmetry breaking SU(2)_L x SU(2)_R -> SU(2)_{L+R} with Goldstones, gauge bosons and one multiplet of vector and axial-vector massive resonance states. Using the dispersive representation of Peskin and Takeuchi and imposing the short-distance constraints dictated by the operator product expansion, we obtain S at the NLO in terms of a few resonance parameters. In asymptotically-free gauge theories, the final result only depends on the vector-resonance mass and requires M_V > 1.8 TeV (3.8 TeV) to satisfy the experimental limits at the 3 \sigma (1\sigma) level; the axial state is always heavier, we obtain M_A > 2.5 TeV (6.6 TeV) at 3\sigma (1\sigma). In strongly-coupled models, such as walking or conformal technicolour, where the second Weinberg sum rule does not apply, the vector and axial couplings are not determined by the short-distance constraints; but one can still derive a lower bound on S, provided the hierarchy M_V < M_A remains valid. Even in this less constrained situation, we find that in order to satisfy the experimental limits at 3\sigma one needs M_{V,A} > 1.8 TeV. dc.language.iso eng dc.relation.ispartof Journal of High Energy Physics, 2012, vol. 2012, num. 106, p. 1-34 dc.rights.uri info:eu-repo/semantics/openAccess dc.source Pich Zardoya, Antonio Rosell Escribà, Ignasi Sanz Cillero, Juan José 2012 One-loop calculation of the oblique S parameter in higgsless electroweak models Journal of High Energy Physics 2012 106 1 34 dc.subject Física dc.title One-loop calculation of the oblique S parameter in higgsless electroweak models dc.type info:eu-repo/semantics/article dc.date.updated 2015-02-26T12:52:33Z dc.identifier.doi http://dx.doi.org/10.1007/JHEP08(2012)106 dc.identifier.idgrec 081680

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