Mass fits for $ B ^0 \rightarrow K^{*0} \mu^+ \mu^-$ decays used to extract the integrated $ C P$ asymmetry. The curves displayed are the full mass fit (blue, solid), the signal peak (red, short-dashed), and the background (grey, long-dashed). The mass fits on the top row correspond to the (a) $ B ^0$ and (b) $\overline{ B }{} ^0$ decays for one magnet polarity, while the bottom row shows the mass fits for (c) $ B ^0$ and (d) $\overline{ B }{} ^0$ for the reverse polarity.

Fitted value of $ {\cal A}_{ C P }$ in $ B ^0 \rightarrow K^{*0} \mu^+ \mu^-$ decays in bins of the $\mu ^+\mu ^-$ invariant mass squared ( $ q^2$ ). The red vertical lines mark the charmonium vetoes. The points are plotted at the mean value of $ q^2$ in each bin. The uncertainties on each $ {\cal A}_{ C P }$ value are the statistical and systematic uncertainties added in quadrature. The dashed line corresponds to the $ q^2$ integrated value, and the grey band is the 1$\sigma$ uncertainty on this value.

Animated gif made out of all figures.

Systematic uncertainties on $ {\cal A}_{ C P }$ , from residual kinematic asymmetries, muon asymmetry, choice of signal model, and the modelling of the mass resolution, for each $ q^2$ bin. The total uncertainty is calculated by adding the individual uncertainties in quadrature.

Values of $ {\cal A}_{ C P }$ for $ B ^0 \rightarrow K^{*0} \mu^+ \mu^-$ in the $ q^2$ bins used in the analysis.