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 s~(1/2)=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.     

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.     

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 chromomagnetic dipole moment (CMDM) ΔK. We find that the contribution of the LHT model is one order of magnitude smaller than the standard model prediction value.     

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.     

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 (A_H) is supposed to be an ideal 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^- → A_HA_Hγ 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 all, it can be a good chance to observe the heavy photon via this process with the high yearly luminosity of the ILC.     

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 ideal 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 all, it can be a good chance to observe the heavy photon via this process with the high yearly luminosity of the ILC.     

Precision Calculations for the T-Odd Quark Pair Production at the CLIC e+e- Linear Collider

We perform the precision calculations for the e⁺e^-→q_q_(q_q_=u_u_, c_c_, d_d_,s_s_) processes up to the QCD next-to-leading order (NLO) including full weak decays for the final T-odd mirror quarks in the littlest Higgs model with T-parity (LHT) at the Compact Linear Collider (CLIC). We show the dependence of the leading order (LO) and NLO QCD corrected cross sections on the colliding energy √s, and provide the LO and QCD NLO kinematic distributions of final particles. The results show that the LO cross section can be enhanced by the NLO QCD correction and the K-factor increases obviously when the threshold of the on-shell q_q_-pair production approaches the colliding energy √s. The K-factor value varies in the range of 1.04 ～ 1.41 in our chosen parameter space. We find that a simple approximation of multiplying the LO kinematic distribution with the integrated K-factor is not appropriate for precision study of the e⁺e^-→q_q_(q_q_=u_u_, c_c_, d_d_,s_s_) processes, since the NLO QCD corrections are phase space dependent. It is necessary to calculate the differential cross sections including full NLO QCD corrections to get reliable results.     

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-Zumino-Witten term, which leads that the lightest T-odd gauge boson A_H decays into the SM particles. First, we examine some lepton flavor violating decays of A_H, namely A_H→τ^±μ^干, A_H→τ^±e^干, and A_H→μ^±e^干. We find that the branching ratios can reach 10^-7 for A_H→τ^±μ^干, 10^-8 for A_H→τ^±e^干, and 10^-8 for A_H→μ^±e^干. 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→q_Hq_H→τ^±μ^干+4 jets, and hardly to be detected for pp→q_Hq_H→τ^±e^干(μ^±e^干)+4 jets and pp→ W_HW_H→τ^±μ^干(τ^±e^干, μ^±e^干)+6 jets.     

小Higgs模型对顶夸克在eγ对撞机上产生的影响

在最小Higgs模型和T宇称下的最小Higgs模型中, 计算了单个顶夸克的产生 过程e^－γ→ν_ebt的产生截面, 并讨论了这两种模型对该过程产生截面的贡献. 发现在合适的参数范围内, 来自T宇称下的最小Higgs模型中对Wtb耦合的修正项对该过程产生截面的相对修正大于5%,这种影响能在将来的直线对撞机实验中探测到. 然而, 在最小Higgs模型中, 新的规范玻色子W±H对该过程的贡献非常小.