Connecting String Theory to Particle Physics at the LHC

The Large Hadron Collider (LHC) has recently turned on and started collecting invaluable physics data. The particle physics community is eager to see which of the recent beyond the Standard Model theories will be discovered at the LHC. Supersymmetry is one of the strongest candidate for the physics beyond the Standard Model. In this thesis, first, we study the possibilities of discovering supersymmetry at the LHC running at 7 TeV center of mass energy and carry out a reach analysis within the mSUGRA parameter space. We generate nonuniversal mSUGRA benchmark models with nonuniversilities in the gaugino sector which satisfy all the current collider, non-collider, as well as dark matter constraints and at the same time are also discoverable with as low as 1 -- 2 fb -1 of integrated luminosity. In the second part of the thesis, we develop a method to determine if the gaugino masses are unified with the help of the LHC data. As a framework to study gaugino masses, we utilize the mirage mediation model which is a string motivated construction that includes mixed gravity and anomaly mediation. We show that up to a 30% non-universality is measurable after just one year of LHC data running at 14 TeV center of mass energy. Finally, we study the collider phenomenology of another string theory motivated model known as deflected mirage mediation. Deflected mirage mediation is an extension of mirage mediation in which gauge-mediated supersymmetry breaking terms are also present and competitive in size to the gravity-mediated and anomaly-mediated soft terms. We compare and show the phenomenological differences between mirage and deflected mirage mediation at the LHC and study the mass hierarchies of the lightest four sparticles within the deflected mirage unification framework.