Scalar top quarks production in polarized photon-photon collisions at ILC

We study pair production of scalar top quarks (stop, t̃_1 ) in polarized photon-photon collisions with the subsequent decay of the top squarks into b quarks and charginos t̃_1 → bχ̃_1^ ± . We simulate this process by using PYTHIA6.4 for an electron beam energy 2E_beam^e = √(s_ee) = 1000 GeV . The energy spectrum of back-scattered photons is generated by CIRCE2 program. A set of criteria for physical variables is proposed which leads to a good separation of stop signal events from top quark pair production, being the main background. These criteria allow us to reconstruct the mass of the top squark, provided that the neutralino mass is known.