No Arabic abstract
The new colored vector-like heavy fermion $T$ is a crucial prediction in little Higgs models, which plays a key role in breaking the electroweak symmetry. The littlest Higgs model is the most economical one among various little Higgs models. In the context of the littlest Higgs model, we study single production of the new heavy vector-like quark via $e^{-}gamma$ collisions and discuss the possibility of detecting this new particle in the TeV energy $e^{+}e^{-}$ collider(LC). We find that the production cross section can vary in a wide range($10^{-3}-10^{1}fb$) in most parameter spaces. For the favorable parameter spaces, the possible signals of the vector-like top quark $T$ can be detected via $e^{-}gamma$ collisions in future $LC$ experiment with $sqrt{s}=3TeV$ and $pounds=500fb^{-1}$.
In the framework of the littlest Higgs($LH$) model and the littlest Higgs model with T-parity($LHT$), We investigate the single top production process $e^{-}gammato u_{e}bbar{t}$, and calculate the corrections of these two models to the cross section of this process. We find that in the reasonable parameter space, the correction terms for the tree-level $Wtb$ couplings coming from the $LHT$ model can generate significantly corrections to the cross section of this process, which might be detected in the future high energy linear $e^{+}e^{-}$ collider($ILC$) experiments. However, the contributions of the new gauge boson $W^{pm}_{H}$ predicted by the $LH$ model to this process is very small.
The littlest Higgs model with discrete symmetry named T-parity(LHT) is an interesting new physics model which does not suffer strong constraints from electroweak precision data. One of the important features of the LHT model is the existence of new source of FC interactions between the SM fermions and the mirror fermions. These FC interactions can make significant loop-level contributions to the couplings $tcV$, and furthermore enhance the cross sections of the FC single-top quark production processes. In this paper, we study some FC single-top quark production processes, $ppto tbar{c}$ and $ppto tV$, at the LHC in the LHT model. We find that the cross sections of these processes are strongly depended on the mirror quark masses. The processes $ppto tbar{c}$ and $ppto tg$ have large cross sections with heavy mirror quarks. The observation of these FC processes at the LHC is certainly the clue of new physics, and further precise measurements of the cross scetions can provide useful information about the free parameters in the LHT model, specially about the mirror quark masses.
In the framework of topcolor-assisted technicolor model we calculate the contributions from the pseudo Goldstone bosons and new gauge bosons to $e^+e^- to tbar{t}$. We find that, for reasonable ranges of the parameters, the pseudo Goldstone bosons afford dominate contribution, the correction arising from new gauge bosons is negligibly small, the maximum of the relative corrections is -10% with the center-of-mass energy $sqrt{s}=500$ GeV; whereas in case of $sqrt{s}=1500$ GeV, the relative corrections could be up to 16%. Thus large new physics might be observable at the experiments of next-generation linear colliders.
With high luminosity and energy at the ILC and clean SM backgrounds, the top-charm production at the ILC should have powerful potential to probe new physics. The littlest Higgs model with discrete symmetry named T-parity(LHT) is one of the most promising new physics models. In this paper, we study the FC processes $e^+e^-(gammagamma)to tbar{c}$ at the ILC in the LHT model. Our study shows that the LHT model can make a significant contribution to these processes. When the masses of mirror quarks become large, these two processes are accessible at the ILC. So the top-charm production at the ILC provides a unique way to study the properties of the FC couplings in the LHT model and furthermore test the model.
The physics prospect at future linear $e^{+}e^{-}$ colliders for the study of the Higgs triple self-coupling via the process of $e^{+}e^{-}to ZHH$ is investigated. In this paper, we calculate the contribution of the new particles predicted by the littlest Higgs model to the cross sections of this process in the future high energy $e^{+}e^{-}$ collider($ILC$). The results show that, in the favorable parameter spaces preferred by the electroweak precision, the deviation of the total cross sections from its $SM$ value varies from a few percent to tens percent, which may be detected at the future $ILC$ experiments with $sqrt{s}$=500GeV.