W_L W_L Scattering in Higgsless Models: Identifying Better Effective Theories

Abstract

The three-site model has been offered as a benchmark for studying the collider phenomenology of Higgsless models. In this paper we analyze how well the three-site model performs as a general exemplar of Higgsless models in describing WLWL scattering, and which modifications can make it more representative. We employ general sum rules relating the masses and couplings of the Kaluza-Klein (KK) modes of the gauge fields in continuum and deconstructed Higgsless models as a way to compare the different theories. We show that the size of the four-point vertex for the (unphysical) Nambu-Goldstone modes and the degree to which the sum rules are saturated by contributions from the lowest-lying KK resonances both provide good measures of the extent to which a highlydeconstructed theory can accurately describe the low-energy physics of a continuum 5d Higgsless model. After comparing the three-site model to flat and warped continuum models, we analyze extensions of the three-site model to a longer open linear moose with an additional U (1) group and to a ring ("BESS' or "hidden local symmetry") model with three sites and three links. Both cases may be readily analyzed in the framework of the general sum rules. We demonstrate that WLWL scattering in the ring model can very closely approximate scattering in the continuum models, provided that the hidden local symmetry parameter 'a' is chosen to mimic ρ-meson dominance of ππ scattering in QCD. The hadron and lepton collider phenomenology of both extended models is briefly discussed, with a focus on the complementary information to be gained from precision measurements of the Z ′ line shape and ZW W coupling at a high-energy lepton collider. SU (2) × SU (2) Higgsless model with a flat extra dimension

Flavor Structure of the Three Site Higgsless Model

“…* ) This U(1) charge assignment causes non-local interactions when we consider the "continuum limit" of the model, however, it can be easily extended to "four-site" by adding an extra U(1) site to cure the problem. (See Ref 24). ) What we should emphasize here is that this U(1) charge assignment is perfectly consistent as a four-dimensional gauged non-linear sigma model.…”

Holographic QCD integrated back to hidden local symmetry

“…In the end, we emphasize that our formulation can be applicable to several types of HQCD models [5,6,32] and models including baryons [18,33]. It will also be interesting to apply our method to HQCD models in hot and/or dense matter [34], and furthermore so-called holographic (walking) technicolor models [35] and Higgsless models [36].…”

Like-sign dilepton signals in Higgsless models at the LHC

“…For a vector state, the dominant production mechanism is the Drell-Yan process, q q → Z 1 , if there are sizable couplings to light quarks [13]. With highly suppressed couplings to light fermions as preferred in Higgsless models, the dominant production channel for Z 1 is commonly considered as the weak boson fusion (WBF) mechanism [5,6,14] pp → Z 1 jj. We extend the calculation by including the the associated production pp → W Z 1 .…”