Quark-flavor-changing Higgs decays from a universal extra dimension

Kaluza–Klein fields characterizing, from a four-dimensional viewpoint, the presence of compact universal extra dimensions would alter low-energy observables through effects determined by some compactification scale, [Formula: see text], since the one-loop level, thus being particularly relevant for physical phenomena forbidden at tree level by the Standard Model. This paper explores, for the case of one universal extra dimension, such new-physics contributions to Higgs decays [Formula: see text], into pairs of quarks with different flavors, a sort of decay process which, in the Standard Model, strictly occurs at the loop level. Finite results, decoupling as [Formula: see text], are calculated. Approximate short expressions, valid for large compactification scales, are provided. We estimate that Kaluza–Klein contributions lie below predictions from the Standard Model, being about 2 to 3 orders of magnitude smaller for compactification scales within [Formula: see text].

Effects of a Single Universal Extra Dimension in Bc→Ds,Dl+l- Decays

The rare semileptonic Bc→Ds,dl+l- decays are studied in the universal extra dimension with a single extra dimension scenario. The sensitivity of differential and total branching ratios and polarization asymmetries of final state leptons to the compactification parameter are presented, for both muon and tau decay channels. Considering the ability of available experiments, it would be useful to study these effects.