Single Top Quark at Future Hadron Colliders. Complete Signal and Background Study

The existence of the top quark has been established in March 1995 by the CDF and DØ collaborations at the Tevatron collider. [1]. Top quark has been discovered in the strong tt̄ pair production mode. The cross section of electroweak process of single top quark was found to be comparable with the QCD pair top production [2]. Single top production mechanism is the independent way of a confirmation of the top quark existence and straightforward key to measure the V tb CKM matrix element and to study the Wtb vertex. Since the mass of the top quark is very large compared to all other quarks one might expect some deviations from the Standard Model (SM) predictions in the top quark interactions [3]. The single top quark production rate is directly proportional to the Wtb coupling and therefore it is a promising place to look for deviations from the SM. However one should stress that the task of background reduction is much more serious and important problem in the case of the single top comparing to the tt̄-pair production. It happens because the jet multiplicity of single top quark events is typically less than for tt̄-pair production and so QCD Wjj and multijet backgrounds are much higher, and the problem of the single top signal extraction is more involved. That is why the detail background study is especially needed in order to find an optimal strategy to search for of single top quark. Top quark decays into a W -boson and a b quark with the almost 100% branching ratio in the framework of the Standard Model. We consider here the subsequent leptonic decays of the W -boson to a electron (muon) and neutrino, as this signal has much less background and should be easier to find experimentally than channels with hadronic decay of the W boson.