number of $X \, b \, \bar{b} \rightarrow \mu^+ \, \mu^+ \, Y$ events is given by $N_b^{++}$ for example. The quoted $a_{SL}^b$ is a combination of the the asymmetry in each $B_q$, denoted $a_{SL}^{bq}$. Each of these contributions to $a_{SL}^b$ can be expressed in terms of the mass and width differences ($M_{12},\Gamma_{12}$) of the $B_q$ meson eigenstates and the CP phase difference between these quantities $\phi_q$ as a\_[SL]{}\^[bq]{} = \_q. Naively one can effect the SM prediction through modifying $M_{12}$ or $\Gamma_{12}$ and both approaches have been explored in the literature. Modifying the decay width significantly [@Dighe:2010nj; @Bauer:2010dg] as an explanation is problematic[^3] and we will focus on MFV NP explanations that involve a NP contribution (that includes a new CP violating phase) to $M^q_{12}$.

The effect of NP on $B_s$ and $B_d$ mass mixing can be parametrized by two real parameters, $h_q>0$ and $\sigma_q$ by writing M\_[12]{}\^q = (M\_[12]{}\^q)\^[SM]{}+ (M\_[12]{}\^q)\^[NP]{}, where the new physics contribution to the mass mixing is related to the standard model value of the mass mixing by, \[hsigma\] (M\_[12]{}\^q)\^[NP]{}=(M\_[12]{}\^q)\^[SM]{} h\_q e\^[2 i \_q]{} . The models we discuss have $h_s = h_d$ and $ \sigma_s = \sigma_d$ which is generally expected in NP models 