Study On The Randall-Sundrun Extra Dimension Effect In Higgs Pair Production At Hadron Colliders

The standard model is one of the most successful theories in the history of physics. It is a gauge theory based on the SU(3)C × SU(2)L × U(1)Y group and unifies the elec-tromagnetic, weak and strong interactions among the four basic interactions in nature. After the discovery of Higgs boson in July 2012, the next main purpose in high energy colliders is the precise test of its properties and finally to verify whether it is the SM Higgs or not. The measurement of couplings of Higgs boson with other SM particles as well as itself is also important to understand the mechanism of electroweak symmetry breaking. In order to measure the couplings of Higgs boson with itself and reconstruct its potential, it is necessary to study the Higgs boson pair production in theory firstly. On the other hand, even though the standard model has achieved great success, it is only an effective theory below the electroweak scale. Therefore the exploration of new physics beyond SM is also important. Among amounts of prospective new physics models, we focus on the Randall-Sundrum (RS) extra dimension model, which is distinctive for tak-ing into consideration the gravity effects at TeV scale. In this work, we study the double Higgs boson production and decay in Randall-Sundrum model at hadron colliders.In RS extra dimension model, We perform the calculations up to QCD next-to-leading order. We use the dimensional regularization scheme to isolate the UV and IR singularities. After performing the renormalization procedure, the virtual correc-tions are UV-finite, while the IR singularities can be canceled exactly by adding the related real emission processes and PDF counterterms. Among them, the IR singulari-ties in the real emission part are separated by using the two cutoff phase space slicing (TCPSS) method. Our numerical results show that the relative RS effect in the vicinities of MHH-M1, M2 (masses of the lightest two Kaluza-Klein (KK) gravitons) or in the central Higgs rapidity region is quite significant. Therefore, with proper kinematic cuts the double Higgs boson production process is promising to detect the RS effect. We also investigate the dependence of the integrated cross section on the RS model param-eters M1 and c0, and find that the integrated cross section is reduced obviously with the increment of the first KK graviton mass M1 or the decrement of the effective coupling C0. Then we consider the Higgs pair production with subsequent Higgs boson decays by employing the narrow width approximation, and present some kinematics distributions of the decay products. We also explore the accompanied SM backgrounds in detecting the RS effect on the pp â†' HH â†'bbÏ„+Ï„-+X process and find that it is possible to extract the RS effect on the signal events from the heavy SM background by choosing proper kinematic cuts on final particles.In summary, the innovation in this thesis is:· We studied the Double Higgs boson production at hadron colliders in the frame of Randall-Sundrum extra dimension model up to QCD next-to-leading order and analysed the dependence of integrated cross section on the RS model parameters for the first time. We consider the subsequent Higgs boson decays and accom-panied SM backgrounds. Our results show that the SM background can be sup-pressed by choosing proper kinematic cuts, which is helpful for detecting the RS effect on the ppâ†'HHâ†'bbÏ„+Ï„-+X process in experiment.