Search for top quark at CDF

There is a vast theoretical and experimental support for idea that op quark as a weak isospin partner to b-quark should exist. Production cross section is steeply falling function of top quark mass. Therefore realistically at present only Tevatron p anti p collider at FNAL, with total energy 1.8 TeV in CMS system, still has a chance of top quark discovery. Dominant production mechanism for top quarks at Tevatron is pair production of t anti t. With almost 100% probability t (anti t) decays in mode t → W+b. Distinct features of this decay provide very good signatures of top quark production which helps to reduce otherwise very high level of background. Based on simple combinatorial arguments one can show that W should decay in 1/9 cases into W → l + ν where l stands for lepton (e,μ,τ). Very clean signature represents case when both W's from t and anti t decay into e (μ) + ν. In this case experimental observation will be two isolated leptons characterized by large transverse momentum, large missing transverse energy ET and 2 b quark jets. Jets originated from b quarks can be quite frequently recognized by presence of secondary vertices associated with jets. Another feature of b-jets which can be used for their identification is frequent association of so called soft leptons with jets. Two experimental setups CDF and D0 are able to take advantage of Tevatron for top quark discovery. Recently CDF collaboration presented evidence for direct observation of t anti t production in 19.3 pb-1 of p anti p collisions at √(s) = 1.8TeV. Very brief account of these results is presented here