Bound on minimal universal extra dimensions from (B)over-bar→Xsγ

We reexamine the constraints on universal extra dimensional models arising from the inclusive radiative (B) over bar -> X-s gamma decay. We take into account the leading order contributions due to the exchange of Kaluza-Klein modes as well as the available next-to-next-to-leading order corrections to the (B) over bar -> X-s gamma branching ratio in the standard model. For the case of one large flat universal extra dimension, we obtain a lower bound on the inverse compactification radius 1/R > 600 GeV at 95% confidence level that is independent of the Higgs mass.