0000000000933960
AUTHOR
José Francisco Oliver Guillén
Aspects of universal extra dimensional models and their latticized versions.
The first part of the thesis deals with models with universal dimensions, models in which all the Standard Model particles propagate in the extra dimension. These models have the interesting property that at low energies there are no tree-level effects of the extra dimensions. Therefore, as long as the new particles are heavy enough, the first effects of the extra dimensions will appear at one loop, and will be suppressed. As a consequence, new particles related with the extra dimensions can be relatively light ( or, equivalently, the extra dimensions relatively large ). It is therefore very important to determine how light those particles could be, and analyze if they can be produced at th…
Universal extra dimensions and Z -> b(b)over-bar
We study, at the one loop level, the dominant contributions from a single universal extra dimension to the process (Z\to b\bar{b}). By resorting to the gaugeless limit of the theory we explain why the result is expected to display a strong dependence on the mass of the top-quark, not identified in the early literature. A detailed calculation corroborates this expectation, giving rise to a lower bound for the compactification scale which is comparable to that obtained from the ρ parameter. An estimate of the subleading corrections is furnished, together with a qualitative discussion on the difference between the present results and those derived previously for the non-universal case.