INSTANTON INDUCED CHARGED FERMION AND NEUTRINO MASSES IN A MINIMAL STANDARD MODEL SCENARIO FROM INTERSECTING D-BRANES

摘要

String instanton Yukawa corrections from Euclidean D-branes are investigated in an effective Standard Model theory obtained from the minimal U(3) x U(2) x U(1) Dbrane configuration. In the case of the minimal chiral and Higgs spectrum, it is found that superpotential contributions are induced by string instantons for the perturbatively forbidden entries of the up- and down-quark mass matrices. Analogous nonperturbative effects generate heavy Majorana neutrino masses and a Dirac neutrino texture with factorizable Yukawa couplings. For this latter case, a specific example is worked out where it is shown how this texture can reconcile the neutrino data.