Lessons from the $B^{0,+}\to K^{*0,+}{\mu }^{+}{\mu }^{-}$ angular analyses

We perform an analysis within the Standard Model of $B^{0,+}\to K^{*0,+}{\mu }^{+}{\mu }^{-}$ decays in light of the recent measurements from the LHCb experiment, showing that new data strengthen the need for sizable hadronic contributions and correlations among them. We then extend our analysis to new physics via the Standard Model effective theory, and carry out a state-of-the-art fit of available $b\to s{\ell }^{+}{\ell }^{-}$ data, including possible hadronic contributions. We find the case of a fully left-handed operator standing out as the simplest scenario with a significance of almost $6\sigma$.

Figure 1

Result from a fit in the SM to the up-to-date experimental $b\to s{\ell }^{+}{\ell }^{-}$ data at low $q^2$ for the binned angular observable $P_5^{\prime }$ [69]. We show the obtained 95% highest probability density interval (HPDI) adopting the parametrization in Eq. (6), together with the most recent measurements from the LHCb angular analyses in [41, 42]. Quark-spectator effects distinguishing the outcome for $B^{0,+}$ decays are at the percent level.

Figure 2

Inference of hadronic contributions from a fit in the SM to the available experimental $b\to s{\ell }^{+}{\ell }^{-}$ dataset at low $q^2$, adopting the parametrization in Eq. (6), omitting (left panel in green) or using (right panel in red) new data from Refs. [41, 42]. Contours correspond to smallest regions of 68%, 95%, 99.7% probability. For marginalized one-dimensional posterior distributions the 68% highest probability density interval (HPDI) is explicitly reported, highlighted by vertical bands.

Figure 3

Left panel: posterior probability density function (p.d.f.) for the NP coefficient $C_{2223}^{LQ}$ in scenario A. Right panel: joint posterior p.d.f for $C_{2223}^{LQ}$ and $C_{2322}^{Qe}$ in scenario B. We show 68%, 95% and 99.7% probability regions in orange, red and green respectively. All results are obtained using the parametrization of hadronic contributions in Eq. (6).