THE RESUMMATION OF TOP QUARK EFFECTS IN THE STANDARD MODEL AND THE 1/Nc EXPANSION

Abstract

It is discussed in the Standard Model how a 1/N _c expansion, where N _c is the number of colors, may be a useful tool for resumming perturbative effects due to a heavy top quark. In particular, some recently proposed formulae for the two-loop resummation of the M_W − M_Z interdependence in terms of m_t are re-obtained and, within the approximation of keeping only the leading term in 1/N _c , it is shown how they are, as a matter of fact, valid to all orders in the top mass.