Unitarisation of WW Scattering and Interpretation of a 2 TeV Resonance in a Strongly Interacting Electroweak Symmetry-Breaking Sector

Abstract

In this work we introduce and combine an effective Lagrangian formalism with the inverse amplitude method to unitarize WLWL ! WLWL and ZLZL ! ZLZL amplitudes in an extended electroweak symmetry breaking sector. We derive the unitarisation method via dispersion relations, and discuss different ways of fnding the possible resonant states. We compare the two amplitudes calculated with the equivalence theorem approximation and with an exact computation. Moreover, since a diboson excess has been observed near 2 TeV |albeit with very limited statistical significance| in WW, WZ and ZZ final states at the LHC experiments, we constrain the Lagrangian low-energy parameters by limiting the region of the parameter space where a resonance around 2 TeV may appear, and also derive the width of these resonances. Computing the cross-section for two processes we get an idea of how the signal varies along the parameter space, and from the amplitudes we introduce unitarized form factors and vertex functions to allow for a proper treatment of the resonances in Monte Carlo generators and a more precise comparison with experiment