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

TL;DR

This paper investigates rare top quark decays within universal extra dimension models, calculating decay rates in minimal and non-minimal scenarios, and discusses their potential observability and constraints from LHC data.

Contribution

It provides a comprehensive one-loop calculation of flavor-changing top decays in both minimal and non-minimal universal extra dimension models, highlighting the impact of boundary localized terms.

Findings

Decay rates in the minimal model are similar to Standard Model predictions.

Non-minimal model can enhance decay rates for specific parameters.

Enhanced decay rates are constrained by LHC search results.

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.