We construct new supersymmetric SU (5) grand unified models based on Z4 × Z2 orientifolds with intersecting D6-branes. Unlike constructions based on Z2 × Z2 orientifolds, the orbifold images of the three-cycles wrapped by D6-branes correspond to new configurations and thus allow for models in which, in addition to the chiral sector in 10 and over(5, ̄) representations of SU (5), only, there can be new sectors with (15 + over(15, -)) and (10 + over(10, -)) vector-pairs. We construct an example of such a globally consistent, supersymmetric model with four-families, two Standard Model Higgs pair-candidates and the gauge symmetry U (5) × U (1) × Sp (4). In an N = 2 sector, there are 5 × (15 + over(15, -)) and 1 × (10 + over(10, -)) vector-pairs, while another N = 1 sector contains one vector-pair of 15-plets. The N = 2 vector-pairs can obtain a large mass dynamically by parallel D6-brane splitting in a particular two-torus. The 15-vector-pairs provide, after symmetry breaking to the Standard Model (via parallel D-brane splitting), triplet pair candidates which can in principle play a role in generating Majorana-type masses for left-handed neutrinos, though the necessary Yukawa couplings are absent in the specific construction. This model can also be interpreted as a flipped SU (5) × U (1)X grand unified model where the 10-vector-pairs can play the role of Higgs fields, though again there are phenomenological difficulties for the specific construction.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics