The impact of universal extra dimensions on B→Xsγ, B→Xs gluon, B→Xsμ+μ-, KL→π0e+e- and ε′/ε

We calculate the contributions of the Kaluza-Klein (KK) modes to the gamma-penguins, gluon-penguins, gamma-magnetic penguins and chromomagnetic penguins in the Appelquist, Cheng and Dobrescu (ACD) model with one universal extra dimension. Together with our previous calculation of Z(0) penguin diagrams [Nucl. Phys. B 660 (2003) 225] this allows to study the impact of the KK modes on the decays B --> X(s)gamma, B --> X-s gluon, B --> X(s)mu(+)mu(-) and K-L --> pi(0)e(+)e(-) and on the CP-violating ratio epsilon'/epsilon. For the compactification scale 1/R = 300 GeV the perturbative part of the branching ratio for B --> X(s)mu(+)mu(-) is enhanced by 12% while the zero in the A(FB) asymmetry is shifted from (s) over cap (0) = 0.162 to (s) over cap (0) = 0.142. The sizable suppressions of Br(B --> X(s)gamma) (20%) and Br(B --> X-s gluon) (40%) could have interesting phenomenological implications on the lower bound on 1/R provided the experimental and theoretical uncertainties will be decreased. Similar comments apply to epsilon'/epsilon that is suppressed relative to the Standard Model expectations with the size of the suppression depending sensitively on the hadronic matrix elements. The impact on K-L --> pi(0)e(+)e(-) is below 10%. We point out a correlation between the zero (s) over cap (0) in the A(FB) asymmetry and Br(B --> X(s)gamma) that should be valid in most models with minimal flavour violation. (C) 2003 Elsevier B.V. All rights reserved.