Probing Universal Extra Dimensions through rare decays induced by $b \to s$ transition

A few $B_{d,s}$ and $\Lambda_b$ decays induced by $b \to s$ transition are studied in the Standard Model and in the framework of the Appelquist, Cheng and Dobrescu (ACD) model, which is a New Physics scenario where a single universal extra dimension is considered. In particular, we investigate the sensitivity of the observables to the radius $R$ of the compactified extra dimension.