No Arabic abstract
Though the predictions of the Standard Model (SM) are in excellent agreement with experiments there are still several theoretical problems, such as fine-tuning and the hierarchy problem. These problems are associated with the Higgs sector of the SM, where it is widely believed that some {it ``new physics} will take over at the TeV scale. One beyond the SM theory which resolves these problems is the Little Higgs (LH) model. In this work we shall investigate the effects of the LH model on $gggg$ scattering; where the process $gggg$ at high energies occurs in the SM through diagrams involving $W$, charged quark and lepton loops (and is, therefore, particularly sensitive to any new physics
Though the predictions of the Standard Model (SM) are in excellent agreement with experiments there are still several theoretical problems associated with the Higgs sector of the SM, where it is widely believed that some ``{it new physics} will take over at the TeV scale. One beyond the SM theory which resolves these problems is the Little Higgs (LH) model. In this work we have investigated the effects of the LH model on $gggg$ scattering cite{Choudhury:2006xa}.
We analyzed the double production and the triple self-coupling of the standard model Higgs boson at future $gamma gamma$ collider energies, with the reactions $gammagamma rightarrow f bar f HH$ $(f=b, t)$. We evaluated the total cross section for $fbar fHH$ and calculated the total number of events considering the complete set of Feynman diagrams at tree-level and for different values of the triple coupling $kappalambda_{HHH}$. We have also analyzed the sensitivity for the considered reaction and we show the results as 95% C.L. regions in the $kappa-M_H$ plane for different values of the center of mass energy and different levels of background. The numerical computation was done for the energies which are expected to be available at a possible Future Linear $gammagamma$ Collider with a center-of-mass energy 500-3000 $GeV$ and luminosities of 1 and $5 ab^{-1}$. We found that the number of events for the process $gammagamma rightarrow t bar t HH$, taking into account the decay products of both $t$ and $H$, is small but enough to obtain information on the triple Higgs boson self-coupling in a independent way, complementing other studies on the triple vertex.
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.
We study heavy physics effects on the Higgs production in $gamma gamma $ fusion using the effective Lagrangian approach. We find that the effects coming from new physics may enhance the standard model predictions for the number of events expected in the final states $bar bb$, $WW$, and $ZZ$ up to one order of magnitude, whereas the corresponding number of events for the final state $bar tt$ may be enhanced up to two orders of magnitude.
We study the process e+e- -->nu nubar gamma to search for its sensitivity to the extra gauge bosons Z_2, Z_3 and W_2 which are suggested by the little Higgs models. We find that the ILC with sqrt(s)=0.5 TeV and CLIC with sqrt(s)=3 TeV cover different regions of the LHM parameters. We show that this channel can provide accurate determination of the parameters, complementary to measurements of the extra gauge bosons at the coming LHC experiments.