Akademik Veri Yönetim Sistemi
PHYSICAL REVIEW D, cilt.72, sa.5, 2005 (SCI-Expanded)
It is known that flavor democracy favors the existence of the fourth standard model (SM) family. In order to give nonzero masses for the first three-family fermions flavor democracy has to be slightly broken. A parametrization for democracy breaking, which gives the correct values for fundamental fermion masses and, at the same time, predicts quark and lepton Cabibbo-Kobayashi-Maskawa (CKM) matrices in a good agreement with the experimental data, is proposed. The pair productions of the fourth SM family Dirac (nu(4)) and Majorana (N-1) neutrinos at future linear colliders with root s=500 GeV, 1 TeV, and 3 TeV are considered. The cross section for the process e(+)e(-)->nu(4)(nu) over bar (4)(N1N1) and the branching ratios for possible decay modes of the both neutrinos are determined. The decays of the fourth family neutrinos into muon channels (nu(4)(N-1)->mu W-+/-(-/+)) provide cleanest signature at e(+)e(-) colliders. Meanwhile, in our parametrization this channel is dominant. W bosons produced in decays of the fourth family neutrinos will be seen in detector as either di-jets or isolated leptons. As an example, we consider the production of 200 GeV mass fourth family neutrinos at root s=500 GeV linear colliders by taking into account di-muon plus four jet events as signatures.