Mass and decays of Brout-Englert-Higgs scalar with extra generations

The higher bound on the mass of the Brout-Englert-Higgs scalar boson (BEH boson for brevity) arising from radiative corrections is not stable when the Standard Model is extended to include non-decoupling particles. In particular additional generations of fermions allow for a heavier scalar. We investigate how the decay branchings of scalar boson are affected by the opening of new channels. The precision measurement of Z-boson parameters, W -boson mass, top quark mass and the value of the running electromagnetic coupling constant at the Z-boson mass allow to predict the mass of the Brout-Englert-Higgs (BEH) boson in the framework of the Standard Model. Table 1 contains the LEPTOP fit of electroweak observables to the experimental data updated in spring 2004. The increase of the t-quark mass according to the D0 reanalysis pushes the scalar boson mass up: (MBEH) 2004 Standard Model = (103 + 54− 39) GeV , (1) and the quality-of-fit is good: χ/nd.o.f. = 16.7/12 . (2) So, in the framework of the 3-generations Standard Model, the central value of MBEH is close to the direct-search lower bound from LEP II, MBEH > 115 GeV. Most probably it