2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/114961In a $Z_{12-I}$ orbifold compactification through an intermediate flipped SU(5), the string MSSM (${\cal S}$MSSM) spectra (three families, one pair of Higgs doublets, and neutral singlets) are obtained with the Yukawa coupling structure. The GUT $\sin^2θ_W^0=\frac38$, even with exotics in the twisted sector, can be run to the observed electroweak scale value by mass parameters of vectorlike exotics near the GUT scale. We also obtain R-parity and doublet-triplet splitting.5 pagesHigh Energy Physics - TheoryAstrophysicsHigh Energy Physics - Phenomenologytext