Constraint on three-Higgs-doublet model parameters by b → sγ decay considering possibility of the fourth generation in quark sector

Weak radiative B-meson decay has been studied to find plausible constraints on the complex coupling constants that arise from the diagonalization of the charged scalar mixing matrix in Weinberg three-Higgs-doublet model considering possibility of the fourth generation in quark sector. We examined the range of these complex coupling constants taking in to account corrections up to leading QCD logarithms, using evolution of fourth-generation CKM matrix with CP violation phase approximately equal to zero. Range of the mass of fourth generation down-type quark b′ and that of fourth-generation uptype quark t′ have been taken with due consideration of the constraint imposed by the present experimental value of theρ parameter keeping in view the mass difference of the fourth-generation quark doublet.