Top Quark Properties in Little Higgs Models
Abstract
Identifying the mechanism which breaks electroweak symmetry and generates fermion masses is one of the main physics goals for both the LHC and the ILC. Studies of the top quark have the potential to illuminate this issue; since it is the heaviest of the Standard Model (SM) fermions, the top is expected to couple strongly to the symmetrybreaking sector. Consequently, the structure of that sector can have significant, potentially observable effects on the properties of the top. for example, it is well known that the vector and axial t{bar t}Z form factors receive large corrections (of order 510%) in certain models of dynamical electroweak symmetry breaking [1]. At future colliders such as the LHC and the ILC, we will be able to pursue a program of precision top physics, similar to the program studying the Z at LEP and SLC. In this manuscript, they study the corrections to the top quark properties in ''Little Higgs'' models of electroweak symmetry breaking [2], and compare the expected deviations from the SM predictions with expected sensitivities of experiments at the LHC and the ILC. In the Little Higgs models, electroweak symmetry is driven by the radiative effects from the top sector, including themore »
 Authors:
 Publication Date:
 Research Org.:
 Stanford Linear Accelerator Center (SLAC)
 Sponsoring Org.:
 USDOE
 OSTI Identifier:
 877519
 Report Number(s):
 SLACPUB11589
hepph/0512053; TRN: US0601544
 DOE Contract Number:
 AC0276SF00515
 Resource Type:
 Conference
 Resource Relation:
 Conference: Presented at 2005 International Linear Collider Physics and Detector Workshop and 2nd ILC Accelerator Workshop, Snowmass, Colorado, 1427 Aug 2005
 Country of Publication:
 United States
 Language:
 English
 Subject:
 43 PARTICLE ACCELERATORS; ACCELERATORS; ACCURACY; FERMIONS; FORM FACTORS; HIGGS MODEL; LINEAR COLLIDERS; PARITY; PHYSICS; PRODUCTION; STANDARD MODEL; SYMMETRY; SYMMETRY BREAKING; T QUARKS; VECTORS; PhenomenologyHEP,HEPEX, HEPPH
Citation Formats
Berger, C.F., /SLAC, Perelstein, M., /Cornell U., CIHEP, Petriello, F., and /Wisconsin U., Madison. Top Quark Properties in Little Higgs Models. United States: N. p., 2005.
Web.
Berger, C.F., /SLAC, Perelstein, M., /Cornell U., CIHEP, Petriello, F., & /Wisconsin U., Madison. Top Quark Properties in Little Higgs Models. United States.
Berger, C.F., /SLAC, Perelstein, M., /Cornell U., CIHEP, Petriello, F., and /Wisconsin U., Madison. Thu .
"Top Quark Properties in Little Higgs Models". United States.
doi:. https://www.osti.gov/servlets/purl/877519.
@article{osti_877519,
title = {Top Quark Properties in Little Higgs Models},
author = {Berger, C.F. and /SLAC and Perelstein, M. and /Cornell U., CIHEP and Petriello, F. and /Wisconsin U., Madison},
abstractNote = {Identifying the mechanism which breaks electroweak symmetry and generates fermion masses is one of the main physics goals for both the LHC and the ILC. Studies of the top quark have the potential to illuminate this issue; since it is the heaviest of the Standard Model (SM) fermions, the top is expected to couple strongly to the symmetrybreaking sector. Consequently, the structure of that sector can have significant, potentially observable effects on the properties of the top. for example, it is well known that the vector and axial t{bar t}Z form factors receive large corrections (of order 510%) in certain models of dynamical electroweak symmetry breaking [1]. At future colliders such as the LHC and the ILC, we will be able to pursue a program of precision top physics, similar to the program studying the Z at LEP and SLC. In this manuscript, they study the corrections to the top quark properties in ''Little Higgs'' models of electroweak symmetry breaking [2], and compare the expected deviations from the SM predictions with expected sensitivities of experiments at the LHC and the ILC. In the Little Higgs models, electroweak symmetry is driven by the radiative effects from the top sector, including the SMlike top and its heavy counterpart, a TeVscale ''heavy top'' T. Probing this structure experimentally is quite difficult. While the LHC should be able to discover the T quark, its potential for studying its couplings is limited [3,4]. Direct production of the T will likely be beyond the kinematic reach of the ILC. However, we will show below that the corrections to the gauge couplings of the SM top, induced by its mixing with the T, will be observable at the ILC throughout the parameter range consistent with naturalness. Measuring these corrections will provide a unique window on the top sector of the Little Higgs. Many Little Higgs models have been proposed in the literature. We will consider two examples in this study, the ''Littlest Higgs'' model [5], and its variation incorporating T parity [6].},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Dec 08 00:00:00 EST 2005},
month = {Thu Dec 08 00:00:00 EST 2005}
}

Little Higgs models provide a natural explanation for the lightness of the Higgs mass. Through the mechanism of collective symmetry breaking, one loop quadratic divergent contributions to the Higgs mass are avoided. In these models a heavy partner of the Top quark appears as required to cancel out the Top's loop contribution. This heavy Top could be produced at the LHC mainly in the single mode. Because of flavor mixing a large FCNC gtT coupling can be generated at one loop that could boost the single T production mode through gg fusion.

Top Quarks and Electroweak Symmetry Breaking in Little Higgs Models
Little Higgs models, in which the Higgs particle arises as a pseudoGoldstone boson, have a natural mechanism of electroweak symmetry breaking associated with the large value of the top quark Yukawa coupling. The mechanism typically involves a new heavy SU(2){sub L} singlet top quark, T. We discuss the relationship of the Higgs boson and the two top quarks. We suggest experimental tests of the Little Higgs mechanism of electroweak symmetry breaking using the production and decay of the T at the Large Hadron Collider. 
Associated production of a single heavy T quark in the littlest and simplest little Higgs models
The colored SU(2){sub L}singlet heavy Tquark is one of the most crucial ingredients in little Higgs models, which is introduced to cancel the largest contribution of the standard model (SM) top quark to the Higgs boson mass at oneloop level. In two representative little Higgs models, the littlest Higgs model and the SU(3) simplest Higgs model, we comprehensively study the single heavy Tquark production at Large Hadron Collider (LHC). After presenting the possibility of relatively light ({approx}500 GeV) Tquark in the simplest little Higgs model, we consider all the relevant processes, the 2{yields}2 process of qb{yields}q{sup '}T, the 2{yields}3 processmore » 
How to rule out Little Higgs (and constrain many other models) at the LHC
In this talk I describe how to discover or rule out the existence of W{prime} bosons at the CERN Large Hadron Collider as a function of arbitrary couplings and W{prime} masses. If W{prime} bosons are not found, I demonstrate the 95% confidencelevel exclusions that can be reached for several classes of models. In particular, W{prime} bosons in the entire reasonable parameter space of Little Higgs models can be discovered or excluded in 1 year at the LHC. 
LHC limits on the topHiggs in models with strong topquark dynamics
LHC searches for the standard model Higgs boson in WW or ZZ decay modes place strong constraints on the topHiggs state predicted in many models with new dynamics preferentially affecting top quarks. Such a state couples strongly to top quarks, and is therefore produced through gluon fusion at a rate enhanced relative to the rate for the standard model Higgs boson. A topHiggs state with mass less than 300 GeV is excluded at 95% C.L. if the associated toppion has a mass of 150 GeV, and the constraint is even stronger if the mass of the toppion state exceeds themore »