Anti-B --> X(s) gamma in two universal extra dimensions

Understand

We calculate the leading order corrections to the anti-B --> X(s) gamma decay in the standard model with two large flat universal extra dimensions.

• We find that the contributions involving the exchange of Kaluza-Klein modes of the physical scalar field a^+-_(kl) depend logarithmically on the ultraviolet cut-off scale Lambda.
• We emphasize that all flavor-changing neutral current transitions suffer from this problem.
• Although the ultraviolet sensitivity weakens the lower bound on the inverse compactification radius 1/R that follows from anti-B --> X(s) gamma, the constraint remains stronger than any other available direct measurement.