Phenomenological Research On New Physics About Top Quark At Hadron Collider

The standard model (SM) of particle physics has testified to be a successfully gauge theoryin describing the fundamental particles and their strong and electroweak interactions.Duringthe past few decades,the standard model has been tested by the large number of precise exper-imental data.But it still has some problems,such as the mass of neutrino and the mechanismof electroweak symmetry breaking(EWSB). It is believed that the SM is a low energy effectivetheory and there must be new theories at higher energy scale around TeV.Therefore,the explo-ration of new physics beyond the SM has become one of the most important tasks in currenthigh energy physics.The top quark is the only fermion with a mass at the electrweak symmetry breaking scalein the SM.Hence the top quark plays a special role in the fundamental particles.It is believedthat the exploration of the top quark will help us to understand the mechanism of electroweaksymmetry breaking and the new physics. There are many top quark events every year at theLHC and that is a good chance for the exploration of top quark physics.So far,the Tevatron has measured some properties of the top quark and find that theforward-backward asymmetry=0.15±0.055in the top pair production shows a2devi-ation from the SM expectation=0.051±0.015.It is assumed that the deviation probablyindicates the existence of the new physics and has been studied in new physics models.In ourwork,we further study the new physics models which have been proposed to explain such adeviation.We investigate the two models which explain theanomaly by FCNC couplingbetween a neutral gauge boson′and up type quarks,the (1) model and the left-right mod-el.We calculate the top quark forward-backward asymmetry at the Tevatron,the FCNC decaysâ†'(=,,) and the like-sign top pair production at the LHC. In the second work,weperform a comparative study for two models: the′model and the color triplet diquark () model.Requiring these models to explain theand also satisfy the top pair production ratemeasured at the Tevatron, we examine their contributions to observables at the LHC such asthe charge and polarization asymmetries in top quark pair productions and′+′(+)productions.