Fermion mass effects at linear colliders

Abstract

A few physical examples are discussed which illustrate a role of fermion masses in the Standard Model predictions for reactions which will be measured at future linear colliders. Taking into account nonzero fermion masses is important not only in the context of the Higgs boson, or the top quark pair production and decay. The mass effects may also become numerically sizable for reactions involving light fermion flavours only. It is interesting that the mass effects do not always disappear in the presence of cuts. In some situations, the cuts may even enlarge the mass effect or make it inverse, i. e. stronger for lighter fermion flavours than for heavier ones.