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

Photon radiation in e+e−→e^+e^-\to hadrons at low energies with CARLOMAT 3.1

We present a sample of results for the cross sections of several processes of low energetic $e^+e^-$ annihilation into final states containing pions accompanied by one or two photons, or a light lepton pair. The results, which have been obtained with a new version of a multipurpose Monte Carlo program CARLOMAT, labelled 3.1, demonstrate new capabilities of the program which, among others, include a possibility of taking into account either the initial or final state radiation separately, or both at a time, and a possibility of inclusion of the electromagnetic charged pion form factor for processes with charged pion pairs. We also discuss some problems related to the $U(1)$ electromagnetic gauge invariance.Comment: 17 pages, 17 figures, matches version published in Eur. Phys. J.