$B \to \gamma \gamma$ in an ACD model

TL;DR

This paper calculates the decay amplitudes for B mesons decaying into two photons within an ACD model, finding cancellations and slight decreases compared to the Standard Model, with potential modest enhancements from QCD corrections.

Contribution

It provides a complete calculation of $B o \gamma \gamma$ amplitudes in an ACD model, improving upon previous incomplete analyses.

Findings

Cancellations between KK tower contributions reduce decay rates.

Predicted decay rates are slightly lower than Standard Model predictions.

QCD corrections might modestly increase branching ratios and CP asymmetries.

Abstract

We present a full calculation of the amplitudes for $B_{d[s]} \to \gamma \gamma$ in a simple ACD model that extends an incomplete one in a previous paper. We find cancellations between the contributions from different KK towers and a small decrease relative to the SM predictions. It is conjectured that radiative QCD corrections might actually lead to an enhancement in the branching ratios and {\bf CP} asymmetries, but no more than modest ones.