Study of Scalar Top Quarks in the Neutralino and Chargino Decay Channel

The scalar top discovery potential has been studied with a full-statistics background simulation at √ s = 500 GeV and L = 500 fb−1 for the TESLA project. The beam polarization is very important to measure the scalar top mixing angle and to determine its mass. The latest estimation of the beam polarization parameters is applied. This study includes e polarization, which improves the sensitivity. For a 180 GeV scalar top at minimum production cross section, we obtain ∆m = 0.8 GeV and ∆cos θt̃ = 0.008 in the neutralino decay channel, and ∆m = 0.5 GeV and ∆cos θt̃ = 0.004 in the chargino decay channel. Talk at the Worldwide Workshop on Future e+e− Collider, Chicago, November 2000, to be published in the proceedings. Study of Scalar Top Quarks in the Neutralino and Chargino Decay Channel H. Nowak and A. Sopczak 1 DESY Zeuthen, 2 University of Karlsruhe The scalar top discovery potential has been studied with a full-statistics background simulation at √ s = 500 GeV and L = 500 fb for the TESLA project. The beam polarization is very important to measure the scalar top mixing angle and to determine its mass. The latest estimation of the beam polarization parameters is applied. This study includes e polarization, which improves the sensitivity. For a 180 GeV scalar top at minimum production cross section, we obtain ∆m = 0.8 GeV and ∆cos θt̃ = 0.008 in the neutralino decay channel, and ∆m = 0.5 GeV and ∆cos θt̃ = 0.004 in the chargino decay channel. Introduction The study of the scalar top quarks is of particular interest, since the lighter stop mass eigenstate is likely to be the lightest scalar quark in a supersymmetric theory. The mass eigenstates are mt̃1 and mt̃2 with mt̃1 < mt̃2 , where t̃1 = cos θt̃ t̃L + sin θt̃t̃R and t̃2 = −sin θt̃t̃L + cos θt̃t̃R with the mixing angle cos θt̃. We study the experimental possibilities to determinemt̃1 and cos θt̃ at a high-luminosity ee linear collider like the TESLA project 1 with polarized e and e− beams. The simulated production process is ee → t̃1 ̄̃ t1 with two decay modes t̃1 → χ̃c and t̃1 → χ̃b. A 100% branching fraction in each decay mode is simulated. The first scalar top decay into a c-quark and the lightest neutralino results in a signature of two jets and large missing energy. The second investigated stop decay mode leads also to large missing energy and further jets from the chargino decay. The neutralino channel is dominant unless the decay into a chargino is kinematically allowed. Details of the event simulation with SGV 2 tuned for a TESLA detector 1 are given in Ref. . The signals and a total of 16 million Standard Model background events are simulated (Table 1) for L = 500 fb. Channel χ̃cχ̃c̄ χ̃bχ̃b̄ eWν WW qq̄ t̄t ZZ eeZ (in 1000) 50 5