Upper Bounds on Supersymmetric Contributions tob→sTransitions fromBs−B¯sMixing

We study the constraints on supersymmetric contributions to $b\to s$ transitions from the recent allowed range and measurement of $B_s-{\overline{B}}_s$ mixing obtained by the D0 and Collider Detector at Fermilab collaborations at the Tevatron. We compute the upper bounds on the relevant off-diagonal squark mass terms and compare them with the bounds coming from $\Delta F=1$ decays. We find that the constraints on chirality-flipping mass insertions are unaffected. Conversely, the measurement of $B_s-{\overline{B}}_s$ mixing is effective in constraining chirality-conserving mass insertions, and it has striking effects in the case in which left- and right-handed insertions have similar size. Finally, we discuss the phase of the $B_s-{\overline{B}}_s$ mixing amplitude in the presence of supersymmetric contributions.