Rare Top Decays in Minimal and Non-minimal Universal Extra Dimension

Abstract

The flavour changing decays of the top quark are severely suppressed in the Standard Model by virtue of the Glashow-Iliopoulos-Maiani mechanism. Many beyond Standard Model extensions predict the decay rates at a level that is observable in the LHC. We perform a complete one-loop calculation of the flavour changing top quark decays $t\to c\gamma$ and $t\to ch$ in the universal extra dimensional model. Apart from considering the decay rates in the minimal version of the model, we also calculate the rates in the non-minimal scenario where the presence of boundary localised terms interestingly modify the set-up. We find that the decay rates in the minimal variant of the model do not change much from their Standard Model values. In the non-minimal version of this model, these decay rates can be higher for specific choices of the boundary localised parameters for a certain range of inverse compactification radius. But these model parameters lead to Kaluza-Klein particle masses that are in tension with various searches at the LHC.

Comments: 31 pages, 11 figures; added more discussion, one section, a few clarifications and minor changes in the text and abstract; fixed typos; updated references; matches published version