Rare Bs decays to η and η' final states

We study exclusive Bs decays to final states with η and η', induced by the rare b→sl+l- and b→sνν transitions. Differential decay rates and total branching fractions are predicted in the standard model, adopting the flavor scheme for the description of the η-η' mixing. We discuss the theoretical uncertainty related to the hadronic matrix elements. We also consider these decay modes in a new physics scenario with a single universal extra dimension, studying the dependence of branching ratios and decay distributions on the compactification scale R-1 of the extra dimension.