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Register a new userPair production of scalar top quarks in e+e- collisions at ILC.
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We study the pair production of scalar top quarks in e+e- collisions with the subsequent decay of the top squarks into b-quarks and charginos. We simulate this process using PYTHIA6.4 for beam energies 2E_beam = 350, 400, 500, 800, 1000 GeV. Proposing a set of criteria we obtain a good separation of the signal stop events from top quark pair production which is the main background. The number of stop production events obtained with the proposed cuts for different energies is calculated for an integrated luminosity of 1000 1/fb. We propose a method to reconstruct the mass of the top squark, provided the mass of the lightest neutralino is known, and estimate the error of the mass determination for the case sqrt{s} = 500 GeV.
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We study pair production of scalar top quarks in polarized photon-photon collisions with the subsequent decay of the top squarks into b-quarks and charginos. We simulate this process by using PYTHIA6.4 for an electron beam energy 2E_beam =1000 GeV. 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.
The scalar top discovery potential has been studied with a full-statistics background simulation for sqrt(s) = 500 GeV and L = 500 fb-1. The simulation is based on a fast and realistic simulation of a TESLA detector. The large simulated data sample allowed the application of an Iterative Discriminant Analysis (IDA) which led to a significantly higher sensitivity than in previous studies. The effects of beam polarization on signal efficiency and individual background channels are studied using separate optimization with the IDA for both polarization states. The beam polarization is very important to measure the scalar top mixing angle and to determine its mass. Simulating a 180 GeV scalar top at minimum production cross section, we obtain Delta(m) = 1 GeV and Delta(cos(theta)) = 0.009.
The effect of virtual electroweak corrections to $e^+e^- rightarrow t bar{t}$ and the contribution of the radiation processes $e^+e^- rightarrow tbar{t}Z, tbar{t}H$ to the inclusive top pair production cross section and forward-backward asymmetry are discussed in the high energy regime.
In the framework of topcolor-assisted technicolor model we calculate the contributions from the pseudo Goldstone bosons and new gauge bosons to $e^+e^- to tbar{t}$. We find that, for reasonable ranges of the parameters, the pseudo Goldstone bosons afford dominate contribution, the correction arising from new gauge bosons is negligibly small, the maximum of the relative corrections is -10% with the center-of-mass energy $sqrt{s}=500$ GeV; whereas in case of $sqrt{s}=1500$ GeV, the relative corrections could be up to 16%. Thus large new physics might be observable at the experiments of next-generation linear colliders.
The physics prospect at future linear $e^{+}e^{-}$ colliders for the study of the Higgs triple self-coupling via the process of $e^{+}e^{-}to ZHH$ is investigated. In this paper, we calculate the contribution of the new particles predicted by the littlest Higgs model to the cross sections of this process in the future high energy $e^{+}e^{-}$ collider($ILC$). The results show that, in the favorable parameter spaces preferred by the electroweak precision, the deviation of the total cross sections from its $SM$ value varies from a few percent to tens percent, which may be detected at the future $ILC$ experiments with $sqrt{s}$=500GeV.
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