There is the Hierarchy problem in the standard model (SM). This problem indicates that there are new physics at energy scale O(TeV). Little Higgs model provides a method that regards Higg particle is a pseudo-Nambu-Goldstone boson (PNGB) to protect the Higgs mass square from quadratic divergences and solves the Little Hierarchy problem. The SU(3) simplest little Higgs model is one of the Little Higgs models. In the original simplest little Higgs model, there is a massless pseudoscalar boson eta, and this massless eta particles will have problems in b-physics and cosmological axion limit. So putting the mu term by hand in simplest little Higgs model to give eta particles mass. The LHC (large hadron collider) is a proton-proton collider machine and start to study physics at 14TeV scale. We calculate the cross section of this process p+p goes to final state t+tbar+eta and see how the signal is in LHC. For calculate the cross section, we get amplitude square from Feynman diagrams then use computer program “FORM” to calculate the trace in amplitude square. We use computer program “vegas” to integrate parton distribution functions in proton and three-body phase space. Finally, we have the cross section.
For coupling constant between eta and top quark is about 0.68, and for eta mass is about 10GeV, we have the cross section of p+p-->t+tbar+eta is about 0.4~0.5 pb.

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