Realistic supersymmetric SU(6)

We present an example of SUSY SU(6) GUT, which predicts an excellent value for αs(MZ)(≃0.119), in comparison with the value αs0(MZ)≃0.126 of minimal SUSY SU(5). A crucial role is played by the vectorlike multiplets from the matter sector, whose masses lie below the GUT scale. For a realistic pattern of fermion masses, the adjoint scalar of SU(6) has VEV along the SU(4)×SU(2)×U(1) direction. This also offers a natural resolution of the doublet-triplet (DT) splitting through the pseudo-Goldstone–Boson mechanism.