Gauge Coupling Unification with Anomalous U(1)_A Gauge Symmetry

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Recently, we proposed a natural scenario of grand unified theories with anomalous U(1)_A gauge symmetry, in which doublet-triplet splitting is realized in SO(10) unification using the Dimopoulos-Wilczek mechanism, and realistic quark and lepton mass matrices can be obtained in a simple way. The scenario has an additional noteworthy feature that the symmetry breaking scale and the mass spectrum of super heavy particles are determined essentially by anomalous U(1)_A charges. Therefore, once all the anomalous U(1)_A charges are fixed, the gauge coupling flows can be calculated. We examine several models in which gauge coupling unification is realized. Examining the conditions for the coupling unification, we show that when all the fields except those of the minimal SUSY standard model become super heavy, the unification scale generically becomes just below the usual GUT scale, Λ_G 〜 2×10^<16> GeV, and the cutoff scale becomes around Λ_G. Since the lower GUT scale leads to a shorter lifetime of nucleons, proton decay via the dimension-six operator, p→e^+π^0, should be observed in future experiments. On the other hand, a cutoff scale lower than the Planck scale may imply the existence of an extra dimension in which only gravity modes can propagate.
理論物理学刊行会の論文
2002-03-25