Reconstruction of Top-Antitop System from 2 Leptons and 2 Jets Final States in Experiment ATLAS

We have tried to reconstruct momenta of both top and antitop from known momenta and masses of products of the decay of these particles. More precisely, we reconstruct top-antitop pair in case of 2 leptons and 2 jets final states. Our method is based on solving the set of equations describing kinematic constraints of this decay. We worked out two tests of this method using event generator PYTHIA; at first on parton level, then using detector response simulator ATLFAST.In most cases we have obtained two solutions from which we have chosen the only with the highest probability.The probability for each solution was computed using angular distribution in central mass system of top-antitop pair together with both neutrinos' energy distributions.The stability of solution can be among others proved by reconstruction of mass of the top.