Flavor-Changing Bottom-Strange Associated in the Littlest Higgs Model with T-parity at the ILC

In the littlest Higgs model with T-parity(LHT) the mirror quarks induce the special flavor structures and some new flavor-changing couplings,which could greatly enhance the production rates of the flavor-changing 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^-→bs andγγ→bs.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 constraints on the relevant parameters of the LHT through the detection of these processes at the ILC.

Top Quark Chromomagnetic Dipole Moment in the Littlest Higgs Model with T-Parity

The littlest Higgs model with T-parity, which is called LHT model, predicts the existence of the new particles, such as heavy top quarks, heavy gauge bosons, and mirror fermions. We calculate the one-loop contributions of these new particles to the top quark ehromomagnetic dipole moment （CMDM） AK. We find that the contribution of the LHT model is one order of magnitude smaller than the standard model prediction value.

Single top partner production in the tZ channel at eγ collision in the littlest Higgs model with T-parity

Introducing the top partner is a common way to cancel the largest quadratically divergent contribution to the Higgs mass induced by the top quark. In this work, we study single top partner production in the tZ channel at eγ collision in the littlest Higgs model with T-parity(LHT). Since it is well known that polarized beams can enhance the cross section, we analyze the signal via polarized electron beams,and photon beams. we have selected two decay modes for comparison, based on the leptonic or the hadronic decays of the W and Z from the top partner. We then construct a detailed detector simulation, and choose a set of cuts to enhance signal significance. For mode A(B), the capacity for exclusion in this process at s1/2=3TeV is comparable to the current experimental limits with L=1000(500) fb-1. If the integrated luminosity can be increased to 3000 fb-1, the top partner mass+mTcan be excluded up to 1350(1440) GeV at 2σ level. We also considered the initial state radiation effect, and find that this effect reduces the excluding ability of the eγ collision on the the top partner mass by approximately 10 GeV. Moreover, the ability to exclude the LHT parameter space at eγ collision complements the existing research.

Rare Higgs three body decay induced by top-Higgs FCNC coupling in the littlest Higgs model with T-parity

Motivated by the search for flavor-changing neutral current（FCNC） top quark decays at the LHC,we calculate the rare Higgs three body decay H→Wbc induced by top-Higgs FCNC coupling in the littlest Higgs model with T-parity（LHT）.We find that the branching ratio of H→Wbc in the LHT model can reach O（10^-7） in the allowed parameter space.

The Lepton Flavor Violating Decays of AHin the Littlest Higgs Model with T-Parity Violation

The T-parity in the littlest Higgs model can be broken by the anomalous Wess-Zumin-Witten term, which leads that the lightest T-odd gauge boson AH decays into the SM particles. First, we examine some lepton flavor violating decays of AH, namely AH → τ±μ±, AH→ τ±e±, and AH→ τ±e±. We find that the branching ratios can reach 10-7 for AH → τ±μ±, 10-s for AH → τ±μ±, and 10-s for AH → τ±e± Then, we study the lepton flavor violating plus jets signatures of the heavy charged gauge boson and mirror quarks at the LHC, and find that it is possible to be detected for pp jets, and hardly to be detected for pp → τ±e± （μ±e±） ＋ 4 jets and p p → W H W H → τ±μ±（ τ±e±,μ±e±） ＋ 6 jets.

Production and decay of the 125 GeV Higgs boson in the littlest Higgs model with T-parity

Motivated by recent search results for the standard model （SM） Higgs boson at the Large Hadron Collider （LHC）, we revisit the Higgs phenomenology in the littlest Higgs model with T-parity （LHT）. We present the signal strength modifier ix, respectively, for the main search channels qq＇→ jjh → jjγγ, qq＇→Vh →Vγγ, qq＇→Vh→ Vbb, gg→ h→ γγ, and gg→h→ VV in the LHT model. It is found that an enhancement factor of 1.09-1.56 in the qq＇→jjh→jjγγ channel can be obtained for this model in Case B with parameter f in the range 500 1000 GeV. However, the rates for bb, ττ are significantly suppressed relative to the SM predictions, which are still consistent with the current sensitivity. It is hoped that this will be further tested with larger integrated luminosity at the LHC.

T-odd top partner pair production in the dilepton final states at the LHC in the littlest Higgs Model with T-parity

In the littlest Higgs model with T-parity, we discuss the pair production of the T-odd top partner （T_） that decays almost 100% into the top quark and the lightest T-odd particle （AH）. Considering the current constraints, we investigate the observability of the T-odd top partner pair production through the process pp→T_T_ →ttAHAH in the final states with two leptons at 14 TeV LHC. We analyze the signal significance and found that the lower limits on the T-odd top partner mass are approximately 1.2 TeV, 1.3 TeV, and 1.4 TeV at the 2or confidence level at 14 TeV LHC with an integrated luminosities of 30 fb^-1, 100 fb^-1, and 300 fb^-1, respectively. This lower limit can be increased to approximately 1.5（1.6） TeV if we used 1000（3000） fb^-1 of the integrated luminosity.

Higgs and Bottom Quarks Associated Production at High Energy Colliders in the Littlest Higgs Model with T-Parity

In the littlest Higgs Model with T-parity,we discuss the Higgs production in association with bottom quarks at the LHC and future electron-positron collider.We calculate the cross sections of production channels pp→bb H,bb→H and bg→b H at 14 Te V LHC and the cross sections of production channel e^+e^-→bb H in(un)polarized beams at the lowest order.In order to investigate the observability,we display some typical final state distributions in the Higgs to diphoton channel.

Associated Production of a Photon with Dark Matter Pair at the ILC within the Littlest Higgs Model with T-parity

Within the context of the Littlest Higgs model with T-parity, the heavy photon （AH） is supposed to be an ideM dark matter （DM） candidate. One direct proof of validity of the model is to produce the heavy photon at collider. In this paper, we investigate the associated production of a photon with heavy photon pair at the planned international e＋ e- linear collider （ILC）, i.e., e＋e- → AHAHγ and show the distributions of the transverse momenta of the photon. The numerical results indicate that the heavy photon production rate could reach severaL fb at the low mass parameter space and the characteristic signal is a single high energetic photon and missing energy, carried by the heavy photons. All in a/l, it can be a good chance to observe the heavy photon via this process with the high yearly luminosity of the ILC.

The littlest Higgs model with T-parity and some lepton flavor violation decay processes

The new particles predicted by the littlest Higgs model with T-parity (called LHT model) can induce the lepton flavor violation (LFV) couplings at the one-loop level,which can add 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 Z → l ˉl and τ-→μ-P 1 P 2 with P 1 P 2 = π + π-,K + K-,and K0 ˉK 0 in the context of this new physics model.We find that the LHT model can indeed make significant contributions to some of these LFV decay processes.The Z factory option for the future high energy e + e-collider experiments will give severe constraints on the LHT model.

Top pair production in the littlest Higgs model with T-parity

In the framework of the littlest Higgs model with T-parity, we study the top pair production at the next generation colliders like LHC and ILC. We find that the order O（αs） corrections to the standard model top pair production cross section at LHC can be very small and the magnitude is below 1%. However, the magnitude of corrections to the standard model top pair production rate at ILC may be over 5% for reasonable values＇of the parameters. Besides this, the corrections to the asymmetry ALR（tt） may be more sizable. Therefore, the top pair production at ILC may serve as a probe of the littlest Higgs model with T-parity, especially the asymmetry ALR（tt）.

Signals of the littlest Higgs model with T-parity at eγ and ep collisions

The littlest Higgs model with T-parity predicts the existence of the neutral, weakly interacting, new gauge boson BH, which can be seen as an attractive dark matter candidate. We study production of the new gauge boson BH via ey and ep collisions. We find that BH can be abundantly produced via the subprocesses e^-T→ L^-BH and γq→BHQ, which might give rise to characteristic signals. Some discussions about the SM backgrounds for this kind of signals are also given.

Littlest Higgs Model and Higgs Boson Associated Production with Top Quark Pair at High Energy Linear e^＋e^- Collider

In the parameter space allowed by the electroweak precision measurement data, we consider the contributions of the new particles predicted by the littlest Higga model to the Higgs hoson associated production with top quark pair in the future high energy linear e^＋e^- collider （ILU）. We find that the contributions mainly come from the new gauge bosons ZH and BH. For reasonable values of the free parameters, the absolute value of the relative correction parameter δσ/σ^SM can be signiticanly large, which might be observed in the future ILU experiment with √S = 800 GeV.

Correction of the Littlest Higgs Model to Higgs Production Process e-γ→veW-H in e-γ Collisions

The littlest Higgs model is the most economical one among various little Higgs models. In the context of the littlest Higgs （LH） model, we study the process e-γ → veW^-H and calculate the contributions of the LH model to the cross section of this process. The results show that in most of the parameter spaces preferred by the electroweak precision data, the value of the relative correction is larger than 10%. Such correction to the process e-γ →veW^-H is large enough to be detected via e-γ collisions in the future high energy linear e^＋ e^- collider （ILC） experiment with the c.m. energy √s = 500 GeV and a yearly integrated luminosity ￡ = 100fb^-1, which will give an idea/way to test the model.

Probing the Lightest New Gauge Boson BH in the Littlest Higgs Model via Processes γγ→f■B_H at ILC

The neutral gauge boson BH with the mass of hundreds GeV is the lightest particle predicted by the littlest Higgs （LH） model, and such particle should be the first signal of the LH model at the planed ILC if it exists indeed. In this paper, we study some processes of the BH production associated with the fermion pair at the ILC, i.e., γγ→ ff^- BH. The studies show that the most promising processes to detect BH amongγγ→ ff^- BH are γγ→ l＇^＋l＇^-BH （l＇ = e,μ）, and they can produce the sufficient signals in most parameter space preferred by the electroweak precision data at the ILC. On the other hand, the signal produced via the certain BH decay modes is typical and such signal can be easily identified from the SM background. Therefore, BH, the lightest gauge boson in the LH model, would be detectable at the photon collider realized at the ILC.

Production of Charged Scalars from the Littlest Higgs Model Associated with Top Quark at LHC

The littlest Higgs （LH） model is the most economical one among various little Higgs models, which predicts the existence of the charged scalars Φ^±. In this paper, we study the production of the charged Higgs boson Φ^- with single top quark via the process gb →tΦ^- at the CERN Large Hadron Collider （LHC）. The numerical results show that the production cross section is sma/ler than 0.2 pb in most of the parameters space, it is very difficult to observe the signatures of the charged scalars via the process pp → gb ＋ X → tΦ^- ＋ X at the LHC experiments. However, it can open a window to distinguish the top-pions in the TC2 model or charged Higgs in the MSSM from Φ^±.

Process e^-у→ e^-H in Littlest Higgs Model

In the context of the littlest Higgs （LH） model, we estimate the production cross section of the process e^-у→ e^-H in the future high-energy linear e^＋e^- collider （ILC） with the center-of-mass （CM） energy √S = 500 GeV. Our numerical results show that the contributions of the LH model Co this process are very small in most of the parameter space allowed by the electroweak precision measurement data, and are very diffcult to be detected in the future ILC experiments.

Muon g - 2 in the Littlest Higgs Model

In this paper the anomalous magnetic dipole moment ofmuon in the littlest Higgs （LH） model is studied at one-loop level. We discuss the dependence of the contributions on the global symmetry breaking scale f, mizing angles c` and , and the Higgs triplet vacuum expectation value v＇ in the electroweak precision data preferring ranges. We find that the LH model can give a relatively small, but non-negligible extra weak contribution to the muon anomalous magnetic moment and can reduce the deviation of △aμ from 2.6σ for the SM to 2.5σ for the LH model.

Top Quark Flavor Changing Decay t→ cH^0 in Little Higgs Model

We study theoretically the quantum effects of the littlest Higgs model (LH) mediated by flavor changing one-loop Feynman diagrams on the rare decay process t → cH0. The comparison of the decay width in the LH model with that in the standard model (SM) is made. We find that the decay branch ratio of t → cH0 in the LH model is at most of the order ～ 10-12, which is two order larger than in the SM. The numerical results show that the difference between the branch ratios in the LH model and the SM is generally sensitive to the LH model parameters, such as symmetry breaking scale f, Higgs boson mass mH0, and x = v'4f /v2 in our chosen parameter space, but relatively insensitive to the value choice of the cosine of the mixing angle c and the ratio λ1/λ2.

宇宙学观测量对小Higgs模型T宇称破缺参数限制的研究

小Higgs模型是高能物理的研究热点之一,但是,最初的小Higgs模型却与弱电精确测量存在着矛盾,因此,人们引入了T宇称。T宇称要求近似守恒或者有着非常小的破缺。这里利用宇宙学观测量对Littest Higgs模型中的T宇称破缺参数进行了严格的限制。