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Register a new userTop Quarks at Photon Colliders
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E.E.Boos
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A review of results on top quark physics expected at the Photon Linear Colliders is presented.
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We investigate the single top quark production with the exchange of unparticles through high energy photon-photon collision $gamma gammato t bar c$. The effects of unparticles on the scattering cross sections for different polarization configurations, and for various values of the scaling dimension $d, 1<d<2$ are analysed. It is shown that the $(+-)$ polarisation configuration is more preferable searching for unparticle physics signatures.
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 present talk is based on the assumption that New Bound States (NBSs) of top-anti-top quarks (named T-balls) exist in the Standard Model (SM): a) there exists the scalar 1S - bound state of 6t+6bar t - the bound state of 6 top-quarks with their 6 anti-top-quarks; b) the forces which bind these top-quarks are very strong and almost completely compensate the mass of the 12 top-anti-top-quarks forming this bound state; c) such strong forces are produced by the interactions of top-quarks via the virtual exchange of the scalar Higgs bosons having the large value of the top-quark Yukawa coupling constant g_tsimeq 1. Theory also predicts the existence of the NBS 6t + 5bar t, which is a color triplet and a fermion similar to the t-quark of the fourth generation. We have also considered b-replaced NBSs: n_b b + (6t + 6bar t - n_b t) and n_b b + (6t + 5bar t - n_b t), etc. We have estimated the masses of the lightest b-replaced NBS: M_{NBS}simeq (300 - 400) GeV, and discussed the larger masses of the NBSs. We have developed a theory of the scalar T-balls condensate, and predicted the existence of the three SM phases, calculating the top-quark Yukawa coupling constant at the border of two phases (with T-balls condensate and without it) equal to: g_t approx 1. The searching for the Higgs boson H and T-balls at the Tevatron and LHC is discussed.
We review some recent developments in top quark production and decay at current and future colliders.
We compute QCD corrections to the production of a ttbar pair in association with a hard photon at the Tevatron and the LHC. This process allows a direct measurement of the top quark electromagnetic couplings that, at the moment, are only loosely constrained. We include top quark decays, treating them in the narrow width approximation, and retain spin correlations of final-state particles. Photon radiation off top quark decay products is included in our calculation and yields a significant contribution to the cross-section. We study next-to-leading order QCD corrections to the ppbar -> ttbar+gamma process at the Tevatron for the selection criteria used in a recent measurement by the CDF collaboration. We also discuss the impact of QCD corrections to the pp -> ttbar+gamma process on the measurement of the top quark electric charge at the 14 TeV LHC.
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