Study of non-minimal SUSY SU(5) model with realistic fermion sectors
  We study a supersymmetric SU(5) model with the extra Higgs multiplets of 45+\bar 45. The unification of the gauge couplings, the fermion masses and the proton lifetime are discussed in details. The dimension-five operators mediated by different colored Higgs sector can be destructive with each other. This effect serves a way of solving the longevity of proton. We analytically analyze this destructive effect in a special limit where the mixing between the 5- and 45-plets is small. Although the theory does not hold in this special limit, it is a revelatory starting point. We can relax this limit and retain the destructive effect. In a generalized parameter space, this model is in accord with experimental results. 
Yunfei Wu and Da-Xin Zhang
hep-ph