  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.
