String Phenomenology in the Era of LHC

The low-energy supersymmetry phenomenology for specific classes of string compactifications is investigated given that the low-energy physics may provide a clue as to the structure of the fundamental theory at high energy scales. The one-parameter model (OPM), a highly constrained subset of minimal Supergravity where all the soft-supersymmetry breaking terms may be fixed in terms of the gaugino mass, is studied, in addition to a three-family Pati-Salam model constructed from intersecting D6-branes. Furthermore, the phenomenology of gravity mediated supersymmetry breaking F-theory SU(5) and SO(10) models, as well as F-SU(5) models with vector- like particles, are examined. We determine the viable parameter space that satisfies all the latest experimental constraints, including the most recent WMAP relic neutralino abundance observations, and find it to be consistent with the CDMS II and other concurrent direct-detection experiments. Moreover, we compute the gamma-ray flux and cross-sections of neutralino annihilations into gamma-rays and compare to the published Fermi-LAT satellite telescope measurements. In F-theory SU(5) and SO(10) models, we predict the exact small deviation of the gaugino mass relation at two-loop level near the electroweak scale, which can be tested at the colliders. More- over, in F-SU(5), we predict the precise deviations from the mSUGRA gaugino mass relations due to the presence of the vector-like particles, also testable at the colliders. The compilation of all these results form a comprehensive collection of predictions with which to evaluate these string models alongside anticipated experimental dis- coveries in the coming decade.