Gauge Coupling Constants Unification In Extra Dimension Model

Abstract

In this thesis, the one loop renormalization group equations for the gauge couplings in the standard model and universal extra dimension were calculated. The universal extra dimension model compactified on the orbifold which has a size 1/R ≈ 1 TeV to yield the 4D standard model. We considered different matter fields localization that is all field have access to the full space time (bulk case), or some of the fields do propagate in extra dimension (brane case). We discussed the evolution of the inverse fine structure constants as function of energy scale in these models and found that as expected the extra dimension lowered the unification scale with respect to the standard model unification scale for different values of the compactification scale . We have shown that in both scenarios (brane and bulk) the gauge couplings are almost unify but do not unify at single energy scale for example with we get an approximate unification at energy scale GeV. We find that there is a difference in the evolution where it increases in the brane case and decreases in the bulk propagating case. Furthermore a successful unification of the three gauge couplings was achieved by introducing three real scalar fields into the extra dimension model in both scenarios. We also discussed the running of Weinberg angle for , and found that can rise from 0.23 to 0.4. This result may be useful, at least from a model building perspective.