Rare t-quark decays t -> cl(j)(+)l(k)(-) and t -> c(nu)over-tilde(j)nu(k) induced by doublets of scalar leptoquarks within the minimal four-color-symmetry model

摘要

The rare t-quark decays t -> cl(j)(+)l(k)(-) and t -> c (nu) over tilde (j)nu(k) induced by scalar-leptoquark doublets are considered within the minimal model involving four-color quark-lepton symmetry and the Higgs mechanism of quark and lepton mass splitting. The partial widths with respect to the decays being considered and the total widths Gamma(t -> cl(+)'l(-)) = Sigma(j,k) Gamma(t -> cl(j)(+)l(k)(-)) and Gamma(t -> c (nu) over tilde'nu) = Sigma(j,k) Gamma(t -> c (nu) over tilde (j)nu(k)) with respect to, respectively, the charged leptonic and neutrino modes are calculated. It is shown that, at scalar-leptoquark masses higher than the t-quark mass (m(S) > m(t)), the branching ratios for these modes are Br(t -> cl(+)'l(-)) approximate to (3.5-0.4) x 10(-5) and Br(t -> c (nu) over tilde'nu) approximate to (7.1-0.8) x 10(-5) at m(S) = 180-250 GeV and an appropriate value of the leptoquark-mixing angle (sin beta approximate to 0.2) and can increase for m(S) < m(t) to Br(t -> cl(+)'l(-)) approximate to 0.03-0.002 and Br(t -> cl(+)'l(-)) approximate to 0.46-0.05 for the charged mode at m(S) = 150-170 GeV for sin beta approximate to 1 and sin beta approximate to 0.2, respectively. In the cases being considered, t-quark decays to pairs of charged leptons can be accessible to detection at LHC. In the last case, these decays could manifest themselves ( for example, in dilepton events) at the Tevatron as well.