Realistic Four-Generation MSSM in Type II String Theory

TL;DR

This paper constructs a four-generation MSSM model within Type II string theory using intersecting D6 branes, demonstrating flavor democracy, mass hierarchies, and gauge coupling unification at the string scale.

Contribution

It presents a novel four-generation MSSM model with nearly equal Yukawa couplings and hierarchical masses derived from string theory constructions.

Findings

Yukawa matrices exhibit flavor democracy with nearly equal couplings.

Hierarchical quark and lepton masses are achievable through small perturbations.

Gauge couplings unify at the string scale.

Abstract

We construct a four-generation MSSM with rank-4 Yukawa matrices from intersecting D6 branes on a T^6/(Z_2 x Z_2) orientifold. The Yukawa matrices obtained provide an example of Flavor Democracy (FD), where the Yukawa couplings are all nearly equal. Mass hierarchies may then be generated by slight perturbations away from FD. We find that it is possible to obtain hierarchical masses for the quarks and leptons of each generation and mixings between them. In addition, the tree-level gauge couplings are unified at the string scale. Finally, we also construct similar models with one, two, and three generations in which the rank of the Yukawa matrices is equal to the number of generations in each model.