Supersymmetric grand unification in SO(14)

We construct a supersymmetric SO(14) model. The matter fields are contained in a 64-dimensional spinor representation Psi. We need many Higgs supermultiplets: phi/sub a/bc( = 364), phi/sub a/bcd( = 1001), phi/sub a/b( = 91), phi/sub a/bcde( = 2002), phi/sub a/bcdef( = 3003). It is possible to obtain the H-bar/sub alphabetagamma/H-bar/sub munurho//sup prime/H-bar/sub sigma/ epsilon/sup alphabetagammamunurhosigma/ term of SU(7) from the phi/sub a/bcdphi/sub abe/phi/sub cde/ term in the SO(14) superpotential, which leads to split multiplets needed to break the SU(2) x U(1) symmetry. In addition, we obtain the desired split multiplet H'/sup alphabeta/ (and H-bar/sub alphabeta//sup prime/) of SU(7) from the phi/sub a/bphi/sub cd/phi/sub abcd/ term of SO(14). It is pointed out that the split multiplet H'/sup alphabeta/ (and H-bar/sub alphabeta//sup prime/) plays an important role for an observable proton decay rate. The global U(1)/sub A/ symmetry is also discussed