Zeros of the W_L Z_L -> W_L Z_L amplitude: where vector resonances stand

TL;DR

This paper investigates how the zeros of the W_L Z_L scattering amplitude can reveal the presence and estimate the mass of vector resonances in a Higgsless electroweak theory, using effective field theory techniques.

Contribution

It introduces a method to identify potential vector resonances and estimate their masses from low-energy electroweak couplings via amplitude zeros analysis.

Findings

Zeros of the amplitude indicate possible vector resonances.

Estimated resonance masses are around 1 TeV.

The approach constrains low-energy couplings consistent with resonances.

Abstract

A Higgsless electroweak theory may be populated by spin-1 resonances around E ~ 1TeV as a consequence of a new strong interacting sector, frequently proposed as a tool to smear the high-energy behaviour of scattering amplitudes, for instance, elastic gauge boson scattering. Information on those resonances, if they exist, must be contained in the low-energy couplings of the electroweak chiral effective theory. Using the facts that: i) the scattering of longitudinal gauge bosons, W_L, Z_L, can be well described in the high-energy region E >> M_W by the scattering of the corresponding Goldstone bosons (equivalence theorem) and ii) the zeros of the scattering amplitude carry the information on the heavier spectrum that has been integrated out; we employ the O(p^4) electroweak chiral Lagrangian to identify the parameter space region of the low-energy couplings where vector resonances may arise. An estimate of their masses is also provided by our method.