Realistic model for SU(5) grand unification
A grand unified model based on SU(5) and supersymmetry is presented. Pairs of superfields belonging to 15 and 15* representations are newly introduced, while gauge coupling unification is satisfied. Improper mass relations in the minimal model between charged leptons and d-type quarks are corrected. Neutrinos have non-vanishing masses, with large angles for generation mixings of the leptons being compatible with the small angles of the quarks. Constraints from proton decay are relaxed. A new source for lepton number generation in the early universe is provided.