Effects Of Extra Dimensions On The Top-pair Production Associated With Higgs Boson At CLIC

The Standard Model (SM) of particle physics has been a very successful model in terms of its effectiveness in explaining a wide variety of quantum field theory concepts as well as serving as a foundation theory for more exotic models that make use of extra dimensions, elaborate symmetries and hypothetical particles. The main deficiency of the Standard Model, however, is its inherent gauge hierarchy (a.k.a. naturalness) prob-lem. This hierarchy problem arises from the divergence of the perturbation series expan-sion of the Higgs mass squared. In an effort to resolve the hierarchy problem, various models have been proposed. Prominent among such models are Supersymmetry (SUSY)models, String Theory models and the Extra Dimensions (ED) models. In the main,Extra Dimensions models come in two kinds: the Arkani-Hamed-Dimopoulos-Dvali(ADD) extra dimensions model and Randall-Sundrum (RS) extra dimensions model.The role of a bulk graviton in predicting the signature of extra dimensions through collider-based experiments is explored in the context of RS Extra Dimensions model.In this present study, gravity effects on Higgs production at the Compact Linear Col-lider (CLIC), using the Randall-Sundrum (RS) extra dimension model, are explored. In particular, the virtual Kaluza-Klein (KK) graviton effects on the e+e-? t(?)H process at centre-of-mass energies (?) = 2.5 TeV and 5 TeV CLIC in the Randall-Sundrum(RS) extra dimension model up to the QCD next-to-leading-order (NLO) are studied.A detailed analysis of the correlations between the integrated cross section and the RS parameters (M1 and c0) is also carried out. The relevant kinematic distributions of the final products in both the Standard Model (SM) and RS model are provided. It is found out that, depending on the colliding energy and the kinematic phase space regions, the internal exchange of the resonant RS KK-graviton generally enhances the SM integrated cross section and the NLO QCD correction can basically suppress the related LO trans-verse momentum and rapidity distributions of the final products. It is further observed that the NLO QCD correction makes peak shifts on the distributions of top-pair invari-ant mass predicted in both models, particularly at the (?)= 5 TeV CLIC. It is concluded that the NLO QCD corrected predictions for the e+e- ? t(?)H process in the RS model not only considerably differ from the corresponding ones in the SM, but also exhibit distinctive distribution performance unlike the corresponding LO results. It is therefore worthwhile exploring the effects of the RS KK-graviton resonance on the t(?)H produc-tion at the future multi-TeV CLIC.The main innovations of this research work are as follows:(i) In the current and future precision Higgs physics, study of the t(?)H production at CLIC up to the QCD NLO, which can not only help verify the Yukawa couplings of the Higgs boson, but also help explore the nature of the electroweak symmetry breaking (EWSB);(ii) Owing to the universal interaction couplings of the warped Kaluza-Klein graviton with the top quark pairs and Higgs boson, study of the e+e- ? t(?)H process in the RS extra dimensions model can further probe the existence of the space's extra dimensions, as well as the TeV gravity and other new physics beyond the SM;(iii) Differing from the hadronic colliders like the LHC, CLIC as a multi-TeV collider takes advantages of the cleaner environment and lower background, thus preci-sion study of the e+e-? t(?)H process within the RS extra dimensions model can be complementary to the high-energy searches at LHC and future HE-LHC.