Speaker
Description
Rare flavour-changing neutral-current decays are powerful probes of the Standard Model and of possible new physics, as they are suppressed in the Standard Model and can receive contributions from virtual heavy particles. The decay $B^0 \to K^{*0}\mu^+\mu^-$ provides a particularly rich channel through its multidimensional angular distribution, from which observables sensitive to the $b \to s\mu^+\mu^-$ transition can be extracted. Previous measurements of angular observables, including $P'_5$, have shown tensions with Standard Model predictions and contribute to the broader pattern of flavour anomalies.
An angular analysis of $B^0 \to K^{*0}\mu^+\mu^-$ decays is being developed using the ATLAS Run-2 proton-proton collision data set collected at $\sqrt{s}=13~\mathrm{TeV}$. Compared with the previous ATLAS Run-1 result, the larger Run-2 data sample is expected to improve the statistical precision of the measurement. The analysis includes the reconstruction and selection of $B^0$ candidates, the implementation of the angular fit model, and the treatment of detector and selection effects through a multidimensional angular acceptance derived from simulation. This contribution reports the current status of the analysis framework and validation studies, and outlines the path towards extracting the angular observables from Run-2 data.