| The Standard Model (SM) of particle physics has obtained tremendous achieve-ments, the search for the scalar Higgs boson, the last unverified SM particle, has also undergone great breakthrough. However, there are defects and problems in the SM itself, one of them is the gauge hierarchy problem caused by the diver-gence of the Higgs mass squared. Up to now, there are various new physics models for solving the gauge hierarchy problem, including the Supersymmetry (SUSY) models, the Littlest Higgs (LH) model and the Extra Dimensions (ED) models. In the ED models, the quantum gravity effects are allowed to appear around the TeV scale, and thus extra dimensions would induce rich phenomenologies at the high-energy colliders. There are mainly two extra dimensons models, i.e., the ADD extra dimensions and RS extra dimensions models, the former is also called the Large Extra Dimensions (LED) model.In the ADD extra dimensions model, we studied the effects of the virtual Kaluza-Klein gravitons on the NLO QCD corrected pp→W+W-→W±l(?) vl(-)+X (I=e,μ) process at the LHC, where the W+W-final states are one of the research focuses in the early LHC era. On the basis of comparison with the published results in the literature, we pointed out and revised their mistakes and improved them, the more reliable results are thus obtained. It was found that: the effects of the virtual Kaluza-Klein gravitons tend to enhance the differential distributions of the invariant mass, and the inclusion of the W-decay can also bring more severe constraint on the fundamental scale MS. Therefore, we conclude that it might be possible for precisely testing the ADD extra dimensions in the NLO QCD corrected pp→W+W-+X process with the W-decay at the LHC.We also investigated the phenomenologies of the W+W-γ/Z productions in the ADD extra dimenions model and the RS extra dimensions model, respec- tively. The W+W-γ/Z final states are also one of the research focuses at the current and future high-energy colliders, including the LHC, ILC and CLIC. Our results showed that:(1) The ADD extra dimensions signal becomes more pro-nounced at the LHC than that at the ILC, especially in the ranges of the high transverse-momentum, large invariant-mass and the central rapidity;(2) At the LHC and CLIC, the RS extra dimensions signal also behaves differently in both the transverse-momentum and rapidity distributions;(3) Compared with the non-resonance performance of the ADD Kaluza-Klein gravitons, the RS Kaluza-Klein gravitons manifest themselves as the TeV-order resonances in the invariant-mass distributions, which arises from the significant dissimilarities between the mass spectra of the ADD Kaluza-Klein gravitons and the RS Kaluza-Klein gravitons.In summary, the innovations in the present dissertation are listed as follows:· In the revisiting of the effects of the ADD extra dimensions on the NLO QCD corrected pp→W+W-→WH±l(?)vl(-)+X (l=e,μ) process at the LHC, we corrected and improved the published results in the literature, we found that the effects of the virtual Kaluza-Klein graviton tend to enhance the invariant-mass distributions, and the inclusion of the W-decay can bring more severe constraint on the fundamental scale MS;· Both the ADD and RS extra dimensions signals have noticeable effects on the kinematic observables, including the transverse-momentum, rapidity and the invariant-mass. Especially, the RS Kaluza-Klein gravitons behave as TeV-order resonance peaks in the invariant-mass distributions, while the ADD Kaluza-Klein gravitons don’t;· In the investigation of the phenomenologies of the extra dimensions’effects on the W+W-γ/Z production, the high energetic LHC and the future ILC and CLIC would play complementary roles, the LHC has a potential advan-tage over the ILC in exploring the ADD extra dimesnions signal, while the CLIC is more suitable than the LHC for studying the RS extra dimensions signal. |
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