Rare t-quark decays t → cl +j l −k and t → cṽ j v k induced by doublets of scalar leptoquarks within the minimal four-color-symmetry model

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The rare t-quark decays t → clj+lk− and t → cṽjkk 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 Γ(t → cl+′l−) = Σj,k Γ(t → clj+lk−) and Γ(t → cl+′l−) = Σj,kΓ(t → cṽjvk) 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 (mS > mt), the branching ratios for these modes are Br(t → cl+′l−) ≈ (3.5−0.4) × 10−5 and Br(t → cṽ′v) ≈ (7.1−0.8) × 10−5 at ms = 180–250 GeV and an appropriate value of the leptoquark-mixing angle (sin β ≈ 0.2) and can increase for mS < mt to Br(t → cl+′l−) ≈ 0.03−0.002 and Br(t → cl+′l−) ≈ 0.46−0.05 for the charged mode at mS = 150–170 GeV for sin β ≈ 1 and sin β ≈ 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.