b→sγdecay inSU(2)L×SU(2)R×U(1)extensions of the standard model

The rare radiative decay $b\to s\gamma$ is studied in ${\mathrm{SU}\mathrm{}\left(2\right)\mathrm{}}_L\times {\mathrm{SU}\mathrm{}\left(2\right)\mathrm{}}_R\times \mathrm{U}\mathrm{}\left(1\right)\mathrm{}$ extensions of the standard model. Matching conditions for coefficients of operators appearing in the low energy effective Hamiltonian for this process are derived, and QCD corrections to these coefficients are analyzed. The new contributions to the radiative transition which arise from the right-handed sector are suppressed by a small mixing angle. But this suppression is offset by a large $\frac{m_t}{m_b}$ helicity flip factor and an enhanced matching condition coefficient function. We thus find that observable deviations from standard model predictions for the $b\to s\gamma$ decay rate can occur in ${\mathrm{SU}\mathrm{}\left(2\right)\mathrm{}}_L\times {\mathrm{SU}\mathrm{}\left(2\right)\mathrm{}}_R\times \mathrm{U}\mathrm{}\left(1\right)\mathrm{}$ theories for a reasonable range of parameter values.