2002/10/21 by Christos Kokorelis, Kokorelis, Christos
Engineering · Physics and Astronomy · #Engineering Applied Research #hep-ph #hep-th
paper · pdf · doi:10.48550/arxiv.hep-th/0210200
46 pages, 2 figures, LaTex
arxiv created 2002/10/21 · arxiv updated 2009/11/30
By employing D6-branes intersecting at angles in D = 4 type I strings, we construct \em five stack string GUT models (PS-II class), that contain at low energy \em exactly the Standard model with no extra matter and/or extra gauge group factors. These classes of models are based on the Pati-Salam (PS) gauge group SU(4)C × SU(2)L × SU(2)R. They represent deformations around the quark and lepton basic intersection number structure. The models possess the same phenomenological characteristics of some recently discussed examples (PS-A and PS-I class) of four stack PS GUTS. Namely, there are no colour triplet couplings to mediate proton decay and proton is stable as baryon number is a gauged symmetry. Neutrinos get masses of the correct sizes. Also the mass relation me = md at the GUT scale is recovered. The conditions for the non-anomalous U(1)'s to survive massless the Green-Schwarz mechanism are equivalent, to the conditions, coming from the presence of N=1 supersymmetry, in sectors involving the presence of \em extra branes and also required to guarantee the existence of the Majorana mass term for the right handed neutrinos. These conditions are independent from the number of \em extra U(1) branes. We also discuss the relative size of the leading worldsheet instanton correction to the trilinear Yukawa couplings in a general GUT model.