$B_s-\bar B_s$ Mixing constraints on FCNC and a non-universal $Z^\prime$

Abstract

$B_s - \bar B_s$ mixing has been measured recently by D0 and CDF. The range predicted in the standard model is consistent with data. However, the standard model central values for $ΔM_{B_s}$ and also $ΔM_ {B_d}$ are away from the data which may be indications of new physics. Using the observed values of $ΔM_{B_s}$ and $ΔM_{B_d}$ we study general constraints on flavor changing $Z^\prime$ interactions. In models with non-universal $Z^\prime$ couplings we find that significant enhancements over the standard model are still possible in the rare decay modes $B\to X_s τ^+ τ^-$, $B\to X_s ν\bar ν$ and $B_s\to τ^+ τ^-$. Tree level $Z^\prime$ contributions to $K\to πν\bar ν$ are now constrained to be very small, but one loop effects can still enhance the standard model rate by a factor of two.