Chirally enhanced corrections to flavor-changing neutral current processes in the generic MSSM

Abstract

Chirally enhanced supersymmetric QCD corrections to flavor-changing neutral current processes are investigated in the framework of the minimal supersymmetric standard model with generic sources of flavor violation. These corrections arise from flavor-changing self-energy diagrams and can be absorbed into a finite renormalization of the squark-quark-gluino vertex. In this way enhanced two-loop and even three-loop diagrams can be efficiently included into a leading-order calculation. Our corrections substantially change the values of the parameters ${\ensuremath{\delta}}_{23}^{d\mathrm{LL}}$, ${\ensuremath{\delta}}_{23}^{d\mathrm{LR}}$, ${\ensuremath{\delta}}_{23}^{d\mathrm{RL}}$, and ${\ensuremath{\delta}}_{23}^{d\mathrm{RR}}$ extracted from $\mathrm{Br}[B\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}]$ if $\mathrm{tan}\ensuremath{\beta}$ is large. We find stronger (weaker) constraints compared to the leading-order result for negative (positive) values of $\ensuremath{\mu}$. The constraints on ${\ensuremath{\delta}}_{13}^{d\mathrm{LR},\mathrm{RL}}$ and ${\ensuremath{\delta}}_{23}^{d\mathrm{LR},\mathrm{RL}}$ from ${B}_{d}\ensuremath{-}{\overline{B}}_{d}$ and ${B}_{s}\ensuremath{-}{\overline{B}}_{s}$ mixing change drastically if the third-generation squark masses differ from those of the first two generations. $K\ensuremath{-}\overline{K}$ mixing is more strongly affected by the chirally enhanced loop diagrams and even subpercent deviations from degenerate down and strange squark masses lead to profoundly stronger constraints on ${\ensuremath{\delta}}_{12}^{d\mathrm{LR},\mathrm{RL}}$.