Flavor-changing interactions with singlet quarks and their implications for the LHC

We investigate the flavor-changing interactions in an extension of the standard model with singlet quarks and singlet Higgs, which are induced by the mixing between the ordinary quarks and the singlet quarks ($q\mathrm{\text{\ensuremath{-}}}Q$ mixing). We consider the effects of the gauge and scalar interactions in the $\ensuremath{\Delta}F=2$ mixings of ${K}^{0}$, ${B}_{d}$, ${B}_{s}$, and ${D}^{0}$ mesons to show the currently allowed range of the $q\mathrm{\text{\ensuremath{-}}}Q$ mixing. Then, we investigate the new physics around the electroweak scale to the TeV scale, which is accessible to the Large Hadron Collider. Especially, the scalar coupling mediated by the singlet Higgs may provide distinct signatures for the decays of the singlet quarks and Higgs particles, which should be compared with the conventionally expected ones via the gauge and standard Higgs couplings. Observations of the singlet quarks and Higgs particles will present us with important insights on the $q\mathrm{\text{\ensuremath{-}}}Q$ mixing and Higgs mixing.