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Title: An effective Higgsless theory: Satisfying electroweak constraints and a heavy top quark

Abstract

The main challenge faced by Higgsless models of electroweak symmetry breaking is to reconcile the experimental constraints imposed by the precision electroweak data and the top quark phenomenology with the unitarity constraints imposed by longitudinal gauge boson scattering amplitudes. In this paper we expand on previous work, giving details of how delocalized fermions can be used to adjust the S parameter to zero, while keeping the T and U parameters naturally suppressed. We also show that it is possible to obtain the top quark mass, without affecting the delay of unitarity violation of the W{sup +}W{sup -}{yields}W{sup +}W{sup -} scattering amplitude, by separating the mass scales of the fermion sector (1/R{sub f}) from that of the gauge sector (1/R{sub g}). The fermion sector scale 1/R{sub f} is only weakly constrained by unitarity of the tt{yields}W{sup +}W{sup -} scattering amplitude; thus the ratio R{sub g}/R{sub f} can be quite large, and the top mass can be achieved easily. Anomalous right-handed couplings involving the third generation quarks also avoid constraints from experimental data if 1/R{sub f} is sufficiently large.

Authors:
;  [1]
  1. Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824 (United States)
Publication Date:
OSTI Identifier:
20782842
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 73; Journal Issue: 7; Other Information: DOI: 10.1103/PhysRevD.73.075011; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; COUPLING; REST MASS; SCATTERING AMPLITUDES; STANDARD MODEL; SYMMETRY BREAKING; T QUARKS; UNITARITY; W MINUS BOSONS; W PLUS BOSONS

Citation Formats

Foadi, Roshan, and Schmidt, Carl. An effective Higgsless theory: Satisfying electroweak constraints and a heavy top quark. United States: N. p., 2006. Web. doi:10.1103/PHYSREVD.73.075011.
Foadi, Roshan, & Schmidt, Carl. An effective Higgsless theory: Satisfying electroweak constraints and a heavy top quark. United States. doi:10.1103/PHYSREVD.73.075011.
Foadi, Roshan, and Schmidt, Carl. Sat . "An effective Higgsless theory: Satisfying electroweak constraints and a heavy top quark". United States. doi:10.1103/PHYSREVD.73.075011.
@article{osti_20782842,
title = {An effective Higgsless theory: Satisfying electroweak constraints and a heavy top quark},
author = {Foadi, Roshan and Schmidt, Carl},
abstractNote = {The main challenge faced by Higgsless models of electroweak symmetry breaking is to reconcile the experimental constraints imposed by the precision electroweak data and the top quark phenomenology with the unitarity constraints imposed by longitudinal gauge boson scattering amplitudes. In this paper we expand on previous work, giving details of how delocalized fermions can be used to adjust the S parameter to zero, while keeping the T and U parameters naturally suppressed. We also show that it is possible to obtain the top quark mass, without affecting the delay of unitarity violation of the W{sup +}W{sup -}{yields}W{sup +}W{sup -} scattering amplitude, by separating the mass scales of the fermion sector (1/R{sub f}) from that of the gauge sector (1/R{sub g}). The fermion sector scale 1/R{sub f} is only weakly constrained by unitarity of the tt{yields}W{sup +}W{sup -} scattering amplitude; thus the ratio R{sub g}/R{sub f} can be quite large, and the top mass can be achieved easily. Anomalous right-handed couplings involving the third generation quarks also avoid constraints from experimental data if 1/R{sub f} is sufficiently large.},
doi = {10.1103/PHYSREVD.73.075011},
journal = {Physical Review. D, Particles Fields},
number = 7,
volume = 73,
place = {United States},
year = {Sat Apr 01 00:00:00 EST 2006},
month = {Sat Apr 01 00:00:00 EST 2006}
}
  • We use conditions for unitarity cancellations to constrain the couplings of the top and bottom quarks to Kaluza-Klein modes in Higgsless models of electroweak symmetry breaking. An example for the mass spectrum of quark resonances in a theory-space model is given and the implications for the collider phenomenology in the top sector are discussed, comparing to signatures of little Higgs and strong electroweak symmetry breaking models.
  • We study the one-loop contributions of the effective flavor changing neutral couplings (FCNC) tcZ, tcH, and tc{gamma} on the electroweak precision observables {gamma}{sub Z},R{sub c},R{sub b},R{sub l},A{sub c}, and A{sub c}{sup FB}, as well as the oblique parameters S and T. Using the known experimental limits on these observables, we may place 95% C.L. bounds on these FCNC couplings which in turn translate into the following limits for the branching ratios BR(t{yields}cZ){<=}1.6x10{sup -2} and BR(t{yields}cH){<=}(0.09-2.8)x10{sup -3} for 114{<=}m{sub H}{<=}170 GeV.
  • We study the combined effects of both strong and electroweak dimension six effective operators on flavor changing top quark physics at the CERN LHC. Analytic expressions for the cross sections and decay widths of several flavor changing processes will be presented, as well as an analysis of the feasibility of their observation at the LHC.
  • The electroweak radiative corrections to [ital O]([alpha][ital m][sub [ital t]][sup 2]/[ital m][sub [ital W]][sup 2]) to the tree-level process [ital t][r arrow][ital H][sup +][ital b] are calculated for a heavy top quark. The corrections imply a few to 10% reduction in the partial width relative to the tree-level result, depending strongly on the parameter tan[beta] and on the top-quark mass. For some given values of tan[beta] and [ital m][sub [ital t]], the combined effect of such electroweak corrections and the QCD corrections can result in a [similar to]17% reduction in the width.
  • The electroweak corrections arising from [ital t]-quark loop and Higgs loop diagrams to the tree-level process [ital H][sup +][r arrow][ital t[bar b]] are calculated in the minimal supersymmetric standard model. Taking into account the additional contributions to [Delta][ital r] arising from the heavy Higgs loops, we present the results in both the [ital G][sub [ital F]] scheme and the [alpha] scheme.