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, $pp\to t\bar{c}$ and $pp\to tV$, 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 $pp\to t\bar{c}$ and $pp\to tg$ 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 littlest Higgs model with T-parity, we studied the contributions of the new particles to the top-quark pair production via $e^{+}e^{-}$ collision at the International Linear Collider. We calculated the top-quark pair production cross section and found this process can generate significantly relative correction. The result may be a sensitive probe of the littlest Higgs model with T-parity.
In the framework of the littlest Higgs model with T-parity (LHT), we study the contributions of the T-even and T-odd particles to the branching ratio R_b. We find that the precision data of R_b can give strong constraints on the masses of T-odd fermions.
We study the top-quark pair production via polarized and unpolarized photon collisions at the International Linear Collider in the context of the littlest Higgs model with T-parity. We calculate the production cross section of the process $γγ\rightarrow t\bar{t}$ and find the effects can be more significant in the $- -$ polarized photon collision mode than in other collision modes, and the relative correction can be expected to reach about -1% in the favorable parameter space.
The Littlest Higgs Model with T parity (LHT) is an interesting alternative model for New Physics at the TeV scale. Although Flavour Physics was not the reason for creating the LHT model, significant effects (such as large CP violation where not predicted by the SM) can be created without violating existing experimental bounds. We study the B-, K- and especially the D-sector.
Motivated by the search for flavor-changing neutral current (FCNC) top quark decays at the LHC, we calculate rare Higgs three body decay $H\rightarrow Wbc$ induced by top-Higgs FCNC coupling in the littlest Higgs model with T-parity(LHT). We find that the branching ratios of $H\rightarrow Wbc$ in the LHT model can reach $\mathcal O(10^{-7})$ in the allowed parameter space.
In this work, we investigate the one-loop QCD correction to top pair production in the littlest Higgs model with T-parity at the LHC. We calculate the relative correction of the top pair production cross section and top-antitop spin correlation at the LHC for $\sqrt{s}=8,14$ TeV. We find that the relative corrections of top pair production cross section can reach about $-0.35\%$, and the top-antitop spin correlation can reach $1.7\%$($2\%$) at the 8(14) TeV LHC in the favorable parameter space.
In this work pair productions of charged and doubly charged scalars in the framework of littlest Higgs model at $e^+e^-$ colliders are studied. In the allowed parameter space of the littlest Higgs model, the production rates of the scalar pairs are calculated. It is obtained that pair productions of charged and doubly charged scalars are reachable at $e^+ e^-$ colliders with energy $\sqrt{S}\geq 1.7TeV$. Using the lepton flavor violating decays of charged scalars calculated in literature, final state analysis is done for pair production processes. This analysis show that depending on the model…
In the littlest Higgs model with T-parity (LHT), we study the $t$-channel single top production in association with a Higgs boson at 8 and 14 TeV LHC. We find that the cross section can be enhanced obviously in this model compared to the Standard Model. By performing a simple parton-level simulation through $pp\rightarrow t(\rightarrow \ell^{+}νb)h(\rightarrow b\bar{b})j$ at 14 TeV LHC, we find that the observability of the signal is promising in the favorable parameter space.
In the littlest Higgs model with T-parity (LHT), the mirror quarks have flavor structures and will contribute to the top quark flavor changing neutral current. In this work, we perform an extensive investigation of the top quark rare three-body decays $t\to cVV (V=γ,Z,g)$ and $t\to cf\bar{f} (f=b,τ,μ,e)$ at one-loop level. Our results show that the branching ratios of $t\to cgg$ and $t\to cb\bar{b}$ could reach $\mathcal {O}(10^{-3})$ in the favorite parameter space of the littlest Higgs model with T-parity, which implies that these decays may be detectable at the LHC or ILC, while for the oth…
In the littlest Higgs model with T-parity, we study associated production of a Higgs and a single top quark at the 14 TeV LHC. We focus on the Higgs to two photons decay and the semileptonic top decay channel. By performing a fast detector simulation, we find that the $thj$ search in the selected channel can excluded the top partner mass $m_{T_{+}}$ up to 805 (857) GeV for case A (case B) at $2σ$ confidence level at 14 TeV LHC with the integrated luminosity $L= 3 \rm ab^{-1}$.
We first study the hadronic lepton flavor violating tau decays within the littlest Higgs model with T-parity (including one or two pseudoscalars, or a vector resonance). We consider the case where only T-odd particles and partner fermions contribute, and also its extension including Majorana neutrinos coming from an inverse seesaw. In both cases our mean values lie only one order of magnitude below current upper limits, strengthening the case of searching for these decays in the quest for new physics.
In the littlest Higgs model with T-parity, the new interactions between the mirror leptons and the Standard Model leptons can induce some lepton flavor violation (LFV) processes at loop level. We study the possibility of the ILC to probe the LFV production processes $e^+e^-(γγ)\rightarrow l_{i}\bar{l}_{j}$. Our results show that the rates of $γγ\rightarrow l_{i}\bar{l}_{j}$ can reach 1 fb in optimal cases after reasonable kinematical cuts, which implies that these processes may be observed at the ILC.
We show that the inverse see-saw is the most natural way of implementing neutrino masses in the Littlest Higgs model with T-parity. The three extra quasi-Dirac neutrinos are needed to cancel the quadratically divergent contributions of the mirror leptons to the Higgs mass. If the T-parity of the heavy neutrino singlets is chosen to be even, their contributions to lepton flavor violating transitions are one-loop finite. The most stringent limits on this scenario result from the non-observation of these transitions. Constraints on neutrino mixing imply an upper bound on the mass of the T-odd mir…
Inspired by the recent CMS $h \to μτ$ excess, we calculate the lepton flavor violating Higgs decay $h \to μτ$ in the littlest Higgs model with T-parity (LHT). Under the constraints of $\ell_i \to \ell_j γ$, $Z \to \ell_i \bar{\ell}_j$ and Higgs data, we find that the branching ratio of $h \to μτ$ can maximally reach $\mathcal O(10^{-4})$. We also investigate the correlation between $h \to μτ$, $τ\to μγ$ and $Z \to μτ$, which can be used to test LHT model at future $e^+e^-$ colliders.
The littlest Higgs model with T-parity (LHT) has new flavor-changing (FC) couplings with the Standard Model (SM) quarks, which do not suffer strong constraints from electroweak precision data. So these FC interactions may enhance the cross sections of some flavor-changing neutral-current (FCNC) processes. In this work, we study the FC top-charm associated productions via $e^{-}γ$ collision at the ILC. We find that the cross sections are sensitive to the mirror quark masses. With reasonable values of the parameters, the cross sections may reach the detectable level and provide useful informatio…
Motivated by the first experimental evidence of meson oscillations in the D system, we study D^0 - \bar D^0 mixing in the Littlest Higgs model with T-parity, we investigate its role in constraining the model parameters and its impact on the most interesting flavour observables. We find that the experimental data are potentially strongly constraining but at present limited by large theoretical uncertainties in the long-distance Standard Model contribution to D^0 - \bar D^0 mixing.
In this work we calculate the leading electroweak (EW) corrections to the anomalous $gt\bar{t}$ coupling in the Littlest Higgs model with T-parity (LHT), by applying the Goldstone boson equivalence theorem. In the LHT model, such electroweak corrections arise from the loop diagrams of heavy fermions and the ``would-be'' Goldstone bosons. We further examine the EW corrections in the top quark pair production via the quark annihilation process at the LHC. The negative EW corrections in the Standard Model are partially canceled by the positive EW corrections from the loops of the new heavy partic…
In the littlest Higgs model with T-parity (LHT) the mirror quarks induce the special flavor structures and some new flavor-changing (FC) couplings which could greatly enhance the production rates of the FC processes. We in this paper study some bottom and anti-strange production processes in the LHT model at the International Linear Collider (ILC), i.e., $e^+e^-\rightarrow b\bar{s}$ and $γγ\rightarrow b\bar{s}$. The results show that the production rates of these processes are sizeable for the favorable values of the parameters. Therefore, it is quite possible to test the LHT model or make som…
We investigate a possibility of precision measurements for parameters of the Littlest Higgs model with T-parity at the International Linear Collider (ILC). The model predicts new gauge bosons which masses strongly depend on the vacuum expectation value that breaks a global symmetry of the model. Through Monte Carlo simulations of production processes of new gauge bosons, we show that these masses can be determined very accurately at the ILC for a representative parameter point of the model. From the simulation result, we also discuss the determination of other model parameters at the ILC.
In this work, we investigate the Higgs-boson production processes $e^{+}e^{-}\rightarrow ZH$, $e^{+}e^{-}\rightarrow ν_{e}\bar{ν_{e}}H$ and $e^{+}e^{-}\rightarrow e^{+}e^{-}H$ in the littlest Higgs model with T-parity. We present the production cross sections, the relative corrections and some distributions of the final states. In the allowed parameter space, we find that the relative corrections of the three production channels are negative, the relative correction of the $ZH$ production can reach $-7.5\%$ and the relative corrections of the $ν_{e}\bar{ν_{e}}H$ and $e^{+}e^{-}H$ production ca…
In the framework of the littlest Higgs Model with T-parity, we discuss the top partner production at future $e^{+}e^{-}$ collider. We calculate the cross sections of the top partner production processes and associated production processes of Higgs and top partner under current constraints. Then, we investigate the observability of the T-odd top partner pair production through the process $e^{+}e^{-}\rightarrow T_{-}\bar{T}_{-}\rightarrow t\bar{t}A_{H}A_{H}$ in the $t\bar{t}$ di-lepton channel for two T-odd top partner mass $m_{T_{-}}$=603(708) GeV at $\sqrt{s}$=1.5 TeV. We analyze the signal s…
Motivated by the recent LHC Higgs data and null results in searches for any new physics, we investigate the Higgs couplings and naturalness in the littlest Higgs model with T-parity. By performing the global fit of the latest Higgs data, electroweak precise observables and $R_{b}$ measurements, we find that the scale $f$ can be excluded up to 600 GeV at $2σ$ confidence level. The expected Higgs coupling measurements at the future collider TLEP will improve this lower limit to above 3 TeV. Besides, the top parnter mass $m_{T_{+}}$ can be excluded up to 880 GeV at $2σ$ confidence level. The futu…
In the littlest Higgs model with T-parity (LHT) the mirror quarks induce the special flavor structures and some new flavor-changing (FC) couplings which could greatly enhance the production rates of the FC processes. We in this paper study some bottom and anti-strange production processes in the LHT model at the International Linear Collider (ILC), i.e., $e^+e^-\to b\bar{s}$ and $γγ\to b\bar{s}$. The results show that the production rates of these processes are sizeable for the favorable values of the parameters. Therefore, it is quite possible to test the LHT model or make some constrains on …
In the Littlest Higgs model with T-parity, the heavy photon ($A_{H}$) is supposed to be a possible dark matter (DM) candidate. A direct proof of validity of the model is to produce the heavy photon at accelerator. In this paper, we study the production rate of $ e^ + e^ - \to A_{H}A_{H}$ at the international $e^ + e^ -$ linear collider (ILC) in the Littlest Higgs model with T-parity and show the distributions of the transverse momenta of $A_{H}$. The numerical results indicate that the heavy photon production rate could reach the level of $10^{-1} fb$ at some parameter space, so it can be a go…
Quark and Lepton Flavour Physics in the Littlest Higgs Model with T-Parity
T宇称的最小希格斯模型（LHT）在夸克和轻子扇区都包含了新的味源和CP破坏。它们起源于新规范玻色子W_H、Z_H和A_H介导的普通费米子与镜像费米子的相互作用。在K_L -> pi ^0 nu {bar nu}、K^+ -> pi^+ nu {bar nu}、CP不对称性S_{psi phi}和轻子味违反衰变中，发现了与标准模型最惊人的偏离。特别是，后者的衰变提供了一个明确的区别LHT模型和MSSM。我们总结了最有趣的结果，三个广泛的分析味道物理的LHT模型。
Lepton flavor violation in tau and mu processes is studied in the littlest Higgs model with T-parity. We consider various asymmetries defined in polarized tau and mu decays. Correlations among branching ratios and asymmetries are shown in the following lepton flavor violation processes: mu+ --> e+ gamma, mu+ --> e+ e+ e-, mu- A --> e- A (A = Al, Ti, Au and Pb), tau+ --> mu+ gamma, tau+ --> mu+ mu+ mu-, tau+ --> mu+ e+ e-, tau+ --> mu+ P (P = pi0, eta and eta'), tau+ --> mu+ V (V = rho0, omega and phi), tau+ --> e+ gamma, tau+ --> e+ e+ e-, tau+ --> e+ mu+ mu-, tau+ --> e+ P, tau+ --> e+ V, tau…
The new particles predicted by the topcolor-assisted technicolor ($TC2$) model and the littlest Higgs model with T-parity (called $LHT$ model) can induce the lepton flavor violation ($LFV$) couplings at tree level or one loop level, which might generate large contributions to some $LFV$ processes. Taking into account the constraints of the experimental data on the relevant free parameters, we calculate the branching ratios of the $LFV$ decay processes $τ^-\toμ^- P_1 P_2 $ with $P_1 P_2$ = $π^+π^-$, $K^+K^-$ and $K^0\bar{K^0}$ in the context of these two kinds of new physics models. We find tha…
Motivated by the current observation of a 125 GeV Higgs boson, we calculate $t\rightarrow cH$ and $t\rightarrow cg(γ)H$ in the unitary gauge in the littlest Higgs model with T-parity(LHT). Due to the large contribution from the new mirror fermions, we find that the branching ratios of $t\rightarrow cH$ and $t\rightarrow cgH$ can be greatly enhanced in the LHT model and maximally reach $\mathcal O(10^{-5})$ in the allowed parameter space. When the mirror fermion mass $M_3 > 2(1.5)$ TeV and the cut-off scale $f=500$ GeV, the process of $pp \to t\bar{t} \to 3b +c +\ell+ \slashed E_{T}^{miss}$ can…
We study lepton flavor violation (LFV) within the Littlest Higgs Model with T parity (LHT) realizing an inverse seesaw (ISS) mechanism of type I. With respect to the traditional LHT, there appear new $\mathcal{O}$(\textcolor{black}{10} TeV) Majorana neutrinos, driving LFV. For $τ\to\ell\ell'\bar{\ell}"$ (including wrong-sign, $\ell=e, μ$) decays and $μ\to e$ conversion in Ti, we get typical rates only one order of magnitude below present bounds ($\ell\to\ell'γ$ can reach the current upper limit) and for $Z\to\barτ\ell$, $μ\to e e \bar{e}$ and conversion in Au, results are within two orders of …
We have calculated the cross section of the process e^+e^- \to γγ\to b\bar{b} in the littlest Higgs model with T parity (LHT). We find that, for the favorable parameters, the total cross section σ(e^+e^- \to γγ\to b\bar{b}) is sensitive to the breaking scale f, mixing parameter x_L, the masses of the mirror quarks m_{Hi}, and the relative correction of the LHT model is a few percent to dozens of percent. The cross section is significantly larger than the corresponding results in the standard model and in the other typical new physics models. Therefore the prediction in the LHT model is quite d…
