Variations of the Hidden Sector in a Realistic Intersecting Brane Model

Recently, we discussed the first example of a phenomenologically realistic intersecting D6-brane model. In this model, the gauge symmetry in the hidden sector is USp(2)_1 x USp(2)_2 x USp(2)_3 x USp(2)_4. However, we find that the USp(2)_1 x USp(2)2 gauge symmetry can be replaced by an U(2){12} gauge symmetry, and/or the USp(2)3 x USp(2)4 gauge symmetry can be replaced by an U(2){34} gauge symmetry since the USp(2)^2 stacks of D6-branes contribute to the same Ramond-Ramond tadpoles as those of the U(2) stacks. Thus, there are three non-equivalent variations of the hidden sector, and the corresponding gauge symmetries are U(2){12} x USp(2)_3 x USp(2)4, U(2){34} x USp(2)1 x USp(2)2, and U(2){12} x U(2){34}, respectively. Moreover, we study the hidden sector gauge symmetry breaking, discuss how to decouple the additional exotic particles, and briefly comment on the phenomenological consequences.