Neutral Gauge Boson Z' And The Spin Correlation Of Top Quark Pair Production

Content: The standard model(SM) of elementary particle describes strong and electroweak interactions. The mechanism of electroweak symmetry breaking(EWSB) remains an open question in current physics despite the SM which has been extensively tested by the high energy experimental data during the past 40 years. SM isn't perfect theory, it can only be effective field theory. There must have new physics beyond the SM. So people provided some new physics models. For example, the supersymmetry(SUSY) theory, topcolor assisted technicolor(TC2) model and so on. Now TC2 model is very prevail.The top quark is the by far heaviest of the six fundamental fermions in the SM. In sectionâ…¡, we disscuss the spin correlation at the Hardon Collider and the International Linear Collider. The result shows that at Tevatron we chose the helicity basis to disscuss the top quark spin correlation. At LHC, we have there decay channels to disscuss the t(?) production. Many proposed models predict the existence of an extra heavy neutral gauge boson, Z′. a Z′is a neutral, colorless, self-adjoint, spin-1 gauge boson . Once found to be a Z′, the next goal will be to determine the couplings to the particles. In sectionâ…¢we introduce two models which predict the existence of a Z′. In sectionâ…£, we introduce the propertity and possible physics goal of the ILC.In this paper, we calculate the contributions of Z′predicted by the TC2 model to the spin configurations of the top quark pair production via the process e^-e⁺→t(?) in the off-diagonal basis. Our numerical results show that Z′exchange can generate significantly corrections to the differential cross sections for the t↑(?)↓and t↓(?)↑states. For 1TeV≤M_z′≤2TeV and cosθ≤0, the values of the relative correction parameters R(t↑(?)↓) and R(t↓(?)↑) are in the ranges of 26%～2.3% and 64%～7.7%, respectively. The production cross section for the like-spin state t↑(?)↑+ t↓(?)↓is non zero induced by Z′exchange.Top quark decays before it hadronizes and the spin information is not spoiled and directly reflect to the distribntions of its decay products. The spin correlation in top quark production and decays is an interesting issue in top quark physics. In the off-diagonal basis, the process e^-e⁺→t(?) induced by the SM has two characteristic feature. One is that the production cross sections for the like-spin states vanish and the other is that the production cross section of the spin state t↑(?)↓(t↓(?)↑) for the left-handed (right-handed) electron beam is dominant. Thus, observation of sizable cross section for the like-spin states and large corrections to the cross sections for the t↑(?)↓and t↓(?)↑states can be seen as signals of new physics beyond the SM.