Electroweak radiative corrections to b --> s gamma

Abstract

Two loop electroweak corrections to b --> s gamma decays are computed. Fermion and photonic loop effects are found to reduce R = BR(b --> s gamma)/BR(b --> c e nu) by 8+-2% and lead to the standard model prediction BR(B --> X_s gamma)=(3.28 +- 0.30)x10^-4 for inclusive B meson decays. Comparison of R^{theory} =(3.04 +- 0.25)x10^-3(1+0.10rho), where rho is a Wolfenstein CKM parameter, with the current experimental average R^{exp}=(2.52+-0.52)x10^-3 gives rho=-1.7+-1.9 which is consistent with -0.21<rho<0.27 obtained from other B and K physics constraints.

Figures (4)

• Figure 1: One loop diagrams which give rise to the radiative decay $b\to s\gamma$.
• Figure 2: (a) An example of vacuum polarization renormalization of $\alpha$ by the fermion loops. (b) Fermionic loop corrections to $b\to s\gamma$. Letters in parentheses label distinct lines from which the photon can be emitted. There is also a contribution from leptons in the $W$ propagator loop.
• Figure 3: Examples of the two-loop diagrams where a virtual photon exchange gives a short-distance logarithmic contribution.
• Figure 4: Examples of electroweak corrections to the decay $b\to ce\nu$.