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

We calculate the contributions of the Kaluza–Klein (KK) modes to the γ-penguins, gluon-penguins, γ-magnetic penguins and chromomagnetic penguins in the Appelquist, Cheng and Dobrescu (ACD) model with one universal extra dimension. Together with our previous calculation of Z0 penguin diagrams [Nucl. Phys. B 660 (2003) 225] this allows to study the impact of the KK modes on the decays B→Xsγ, B→Xs gluon, B→Xsμ+μ− and KL→π0e+e− and on the CP-violating ratio ε′/ε. For the compactification scale 1/R=300 GeV the perturbative part of the branching ratio for B→Xsμ+μ− is enhanced by 12% while the zero in the AFB asymmetry is shifted from ŝ0=0.162 to ŝ0=0.142. The sizable suppressions of Br(B→Xsγ) (20%) and Br(B→Xs 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 ε′/ε 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 KL→π0e+e− is below 10%. We point out a correlation between the zero ŝ0 in the AFB asymmetry and Br(B→Xsγ) that should be valid in most models with minimal flavour violation.