Explaining fermions mass and mixing hierarchies through U(1)X and Z2 symmetries

For understanding the hierarchies of fermion masses and mixing, we extend the Standard Model (SM) gauge group with U(1)X and Z2 symmetry. The field content of the SM is augmented by three heavy right-handed neutrinos, two new scalar singlets, and a scalar doublet. U(1)X charges of different fields are determined after satisfying anomaly cancellation conditions. In this scenario, the fermion masses are generated through higher-dimensional effective operators with O(1) Yukawa couplings. The small neutrino masses are obtained through type-1 seesaw mechanism using the heavy right-handed neutrino fields, whose masses are generated by the new scalar fields. We discuss the flavour-changing neutral current processes that arise due to the sequential nature of U(1)X symmetry. We have written effective higher-dimensional operators in terms of renormalizable dimension-four operators by introducing vector-like fermions.