Production of the new gauge boson BH via e－ collision in the littlest Higgs model

The lightest new gauge boson B_H with mass of hundreds GeV is predicted in the littlest Higgs model. B_H should be accessible in the planned ILC and the observation of such particle can strongly support the littlest Higgs model. The realization of γγ and e^－γ collisions would open a wider window to probe B_H. In this paper, we study the new gauge boson B_H production processes e－γ→e－γ     

Searching for Flavor-Changing Neutral-Current Signals via e＋e-（γγ） →tcht0 in Topcolor-Assisted Technicolor Model

In the context of the top-color-assisted technicolor （TC2） model, the flavor-changing neutral-current （FCNC） interaction induced by the top-higgs （hOt） are predicted at tree level. We study the relevant processes of e＋e-（γγ）→tcht0 at the International Linear Collider （ILC）. It is found that these rare processes production rates can be enhanced significantly in the TC2 model. Especially for the process γγ→tcht0, the total cross section will reach a few fb in the reasonable parameter space. We also calculate the distributions of transverse momenta, pseudo-rapid and invariant mass of the top-higgs. In view of the main decay modes of top-higgs for mho 〈 2mr, we find that there will be several hundreds FCNC events produced at the ILC with annually integral luminosity of 500 fb-1. Due to the clean background, such FCNC signals can possibly be detected at the ILC.     

Pair Production of the Doubly Charged Leptons Associated with a Gauge Boson γ or Z in e~+e~-and γγ Collisions at Future Linear Colliders

In this paper,we investigate the production of a pair of doubly charged leptons associated with a gauge boson V(γ or Z) at future linear colliders via e~+e~-and γγ collisions.The numerical results show that the possible signals of the doubly charged leptons may be detected via the processes e~+e~→VX~(++)X~(--)and γγ→VX~(++)X~(--)at future ILC or CLIC experiments.     

Flavor Changing Top Quark Decay and Bottom-Strange Production in the Littlest Higgs Model with T-parity

Flavor changing effects on the processes t → ch, e+e- → bs, e+e-→ bsh and pp → bs in the LHT model are investigated in this paper. We calculate the one-loop level contributions from the T-parity odd mirror fermions and gauge bosons. The results show that the top quark rare decay t → ch in the LHT model can be significantly enhanced relative to that in the SM. The bs production at linear colliders in the LHT model can enhance the SM cross section a lot and reach 0.1 fb in some parameter space allowed in the experiment. But the heavy gauge boson and mirror fermion loops have small contribution to the processes pp → bs and e+e-→ bsh. So the LHT effect on e+e-→ bs might be detected at future linear colliders, while it is too small to be seen for the e+e-→ bsh and pp → bs processes at future linear colliders and LHC.     

Study of new boson W_1~± in the Minimal Higgsless Model at the LHC

The Minimal Higgsless Model predicts the existence of new vector gauge boson W1± . By the process PP → W1± qq → W±Z0qq, Z0 → l+l-, W±→ qq (l=e,μ; q is hadronized to be jets), we study the sensitivity of searching for this possible vector gauge boson in the level of generator events of signal and backgrounds, then give integrated luminosity required to discover 5σ signal as a function of W1± mass. The generator for the signal PP→W1± qq→W±Z0qq at tree level is developed with the Minimal Higgsless Model and th...     

Study of new boson W_1~± in the Minimal Higgsless Model at the LHC

The Minimal Higgsless Model predicts the existence of new vector gauge boson W1± . By the process PP → W1± qq → W±Z0qq, Z0 → l+l-, W±→ qq (l=e,μ; q is hadronized to be jets), we study the sensitivity of searching for this possible vector gauge boson in the level of generator events of signal and backgrounds, then give integrated luminosity required to discover 5σ signal as a function of W1± mass. The generator for the signal PP→W1± qq→W±Z0qq at tree level is developed with the Minimal Higgsless Model and then interfaced with PYTHIA for the parton showers and hadronization. The backgrounds are produced with MadGraph and PYTHIA.     

The single neutral top-higgs production at LHC and ILC in the Topcolor-Assisted Technicolor Model

In this paper, we study the single neutral top-higgs (h0t) production processes at the CERN Large Hadron Collider (LHC) and the International Linear Collider (ILC). At the LHC, the production rates of processes pp→Z(W)h0t are too small to detect h0t . However, with the reasonable parameter values, the cross sections can reach the level of 102 fb for qq→qqh0t process and 103 fb for top quark associated production process pp→th0t+X, respectively. At the ILC, we study the single top-higgs production processes e-γ→νeW-h0t and γγ→W+W-h0t in e-γ and γγ collisions. It is found that the production cross sections can reach the level of a few fb with reasonable parameter values. Furthermore, such processes with the flavor-changing decay mode h0t→tc might provide typical signatures to detected the top-higgs. Therefore, it is hopeful to find the signal of top-higgs at the LHC and ILC experiments via theses processes and test the TC2 model directly.     

Associated production of a neutral top-Higgs with a heavy-quark pair in the γγ collisions at ILC

We have studied the associated production processes of a neutral top-Higgs in the topcolor assisted technicolor model with a pair of heavy quarks in γγ collisions at the International Linear Collider (ILC). We find that the cross section for ttht in γγ collisions is at the level of a few fb with the c.m. energy √s=1000 GeV, which is consistent with the results of the cross section of ttH in the standard model and the cross section of tth in the minimal supersymmetric standard model. It should be clear that hundreds of to thousands of ht per year can be produced at the ILC. This process of γγ→ttht is really interesting in testing the standard model and searching the signs of technicolor.     

Associated production of a neutral top-Higgs with a heavy-quark pair in the γγ collisions at ILC

We have studied the associated production processes of a neutral top-Higgs in the topcolor assisted technicolor model with a pair of heavy quarks in γγ collisions at the International Linear Collider （ILC）. We find that the cross section for ttht in γγ collisions is at the level of a few fb with the c.m. energy √s=1000 GeV, which is consistent with the results of the cross section of ttH in the standard model and the cross section of tth in the minimal supersymmetric standard model. It should be clear that hundreds of to thousands of ht per year can be produced at the ILC. This process of γγ→ttht is really interesting in testing the standard model and searching the signs of technicolor.     

Probing the scale of new physics in the ZZγ coupling at e~+e~- colliders

The Z Zγtriple neutral gauge couplings are absent in the Standard Model(SM)at the tree level.They receive no contributions from dimension-6 effective operators,but can arise from effective operators of dimension-8.We study the scale of new physics associated with such dimension-8 operators that can be probed by measuring the reaction e~+e~-→Zγ followed by ■ decays,at future e~+e~- colliders including the CEPC,FCC-ee,ILC and CLIC.We demonstrate how angular distributions of the final-state mono-photon and leptons can play a key r?le in suppressing SM backgrounds.We further demonstrate that using electron/positron beam polarizations can significantly improve the signal sensitivities.We find that the dimension-8 new physics scale can be probed up to the multiTeV region at such lepton colliders.     

SU（3） Simple Group Model and New Z＇ Properties in Future Linear Colliders

In the SU（3） simple group model, the new neutral gauge boson Z＇ couples to pairs of SM fermions with couplings fixed in terms of the SM gauge couplings and depending only on the choice of the fermion embedding. In this paper, we calculate the contributions of this new particle to the processes e^＋e^-→l^＋l^-, bb^-, and cc^- and study the possibility of detecting this new particle via these processes in the future high-energy linear e^＋e^- collider（LC） experiments with √s= 500 GeV and ￡int= 340 fb^-1. We find that the new gauge boson Z＇ is most sensitive to the process e^＋e^-→b^＋b^-. As long as Mz,≤2 TeV , the absolute values of the relative correction parameter are larger than 5%. We calculate the forward-backward asymmetries and left-right asymmetries for the process e^＋e^-→c^＋c^-, with both the universal and anomaly-free fermion embeddings. Bounds on Z＇ masses are also estimated within 95% confidence level.     

Study of new boson W±1 in the Minimal Higgsless Model at the LHC

The Minimal Higgsless Model predicts the existence of new vector gauge boson W1^±, By the process PP →W1^±qq →W^±Z^0qq, Z^0→ 1^＋1^-, W^±→ qq （1=e,μ; q is hadronized to be jets）, we study the sensitivity of searching for this possible vector gauge boson in the level of generator events of signal and backgrounds, then give integrated luminosity required to discover 5σ signal as a function of W1^± mass. The generator for the signal PP → W1^±qq →W^±Z^0qq at tree level is developed with the Minimal Higgsless Model and then interfaced with PYTHIA for the patton showers and hadronization. The backgrounds are produced with MadGraph and PYTHIA.     

The lepton flavor violating signal of the extra gauge boson Z′in photon-photon collision at the ILC

The hitherto unconstrained lepton flavor mixings,induced by the new gauge boson Z ,which are the prediction of many new physics models,such as topcolor-assisted technicolor (TC2) models and flavor-universal TC2 models,may lead to the lepton flavor violating productions of τμˉ,τeˉ and μeˉ in photon-photon collision at the proposed International Linear Collider (ILC).Through a comparative analysis of these processes,we find that the better channel to probe the new physics models is the production of τμˉ or τeˉ which occurs at a much higher rate than μeˉ production due to the large mixing angle and the large flavor changing coupling,and may reach the detectable level of the ILC for a large part of the parameter space.Since the rates predicted by the Standard Model are far below the detectable level,these processes may serve as a sensitive probe for such new physics models.     

Bounds on the magnetic moment of the τ-neutrino via the process e~ e-→νγ

Using Breit-Wigner resonance relation, bounds on the magnetic moment of the tau-neutrino are calculated through the reaction e e-→νγ at the neutral boson pole in the framework of a superstring-inspired E6 model which has one extra low-energy neutral gauge boson and a LRSM.     

Higgs and Single Top Associated Production at the LHC in the Left-Right Twin Higgs Model

In the framework of the left-right twin Higgs(LRTH) model, we study the Higgs boson and single top quark associated production at the LHC. We investigate the processes pp → thj, pp → thˉb and pp → th W at the 8(14) Te V LHC and find that the production cross sections of the three processes can be enhanced at different levels. Among them,the production cross section of the process pp → thˉb is enhanced significantly due to the contribution of the new particles predicted by the LRTH model.     

Rare Decay Process K→πvv^- in Three-Site Higgsless Model]

Rare decay processes K→πvv^- and KL→π^0vv^- are considered in the framework of three-site Higgsless model. The contributions of this new physics model to these two decay processes come from the new heavy gauge bosons and the correction terms for the couplings of the ordinary gauge bosons with fermions. Our numerical results show that the branching ratios of these two decay processes can be enhanced by 40% and 50% relative to those predicted by the standard model.     

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.     

Production and decay of the 125 GeV Higgs boson in thelittlest 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 μ, 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.     

Effects of the littlest Higgs model on the process e~+ e~- → μ~+ μ~- at a Z~0-factory

We investigate the possibilities of finding the effects of the littlest Higgs (LH) model on the process e + e - →μ + μ - at the leadingorder at a possible Z 0-factory.We study the impacts of the LH model on the observables,such as,the total cross section,the distribution of the transverse momentum of μ-,and the forward-backward charge asymmetry of μin polarized and unpolarized electron-positron collision modes.Besides,we analyze the relations between the observables and the LH model parameters,and discuss the observables of process e + e→μ + μ-in different incoming electron-positron polarization modes.We conclude that one could observe the effects contributed by the LH model on the process e + e-→μ + μin a reasonable parameter space,or might put more stringent constraints on the LH parameters in the future experiments at the possible Z 0-factory.     

Single Production of Heavy Top Quark from Three-Site Higgsless Model

We consider single production of the heavy top quark T predicted by the three-site Higgsless model in future high energy collider experiments, such as the high energy linear e＋ e- collider （ILC）, the linear-ring type ep collider （THERA）, and the CERN Large Hadron Collider （LHC）. Our numerical results show that the possible signals of the heavy top quark T might be detected via the subproeess qb → q＇T at the LHC.