Studying top quark pair production at a linear collider with a program 'eett6f'

Some features of a program 'eett6f' for top quark pair production and decay into six fermions at linear colliders are discussed. Lowest order standard model predictions for cross sections of some six fermion channels and for the top quark decay width are confronted with the predictions obtained within a model with an anomalous Wtb coupling. The question of wether non doubly resonant background can easily be reduced by imposing kinematical cuts is addressed.Comment: 10 pages, 8 figures, presented at the Cracow Epiphany Conference on Heavy Flavors,Cracow, Poland, January 3--6, 200

Anomalous Wtb coupling at the LHC

Some distributions of the mu- in the top quark pair production reaction pp -> b u anti-d anti-b mu- anti-nu_mu at the LHC are calculated to leading order in the presence of the anomalous Wtb coupling with operators of dimension up to five. The distributions in the transverse momentum, rapidity and cosine of the mu- angle with respect to the beam in the laboratory frame and with respect to the reversed momentum of the b-quark in the rest frame of W-boson are changed rather moderately by the anomalous Wtb coupling. The distributions computed with the full set of leading order Feynman diagrams practically do not differ from those computed with the t anti-t production diagrams, with typical acceptance cuts. This demonstrates very little effect of the off resonance background contributions.Comment: 17 pages, 7 figures, version accepted for publication in Acta Physica Polonica

Secondary lepton distributions as a probe of the top--higgs coupling at the LHC

The differential distributions in rapidity and angles of the secondary lepton in the associated production of the top quark pair and higgs boson in proton-proton collisions at the LHC are quite sensitive to the top-higgs coupling. However, the effects of anomalous couplings of the most general t anti-t h interaction with operators of dimension-six that are clearly visible in the signal of the associated production of the top quark pair and higgs boson are to large extent obscured by the background sub-processes with the same final state. This means that analyses of such effects, in addition to higher order corrections that are usually calculated for the on-shell top quarks and higgs boson, should include their decays and possibly complete off resonance background contributions to the corresponding exclusive reactions.Comment: 12 pages, 6 figures, version accepted for publication in JHE