Towards New Frontiers with $B\to \pi K$ Decays

Exploring correlations between the CP asymmetries of $B_d^0\to {\pi }^0{K}_{\mathrm{S}}$ following from an isospin relation, we uncover new tensions with the Standard Model in data for neutral $B\to \pi K$ decays. Should this intriguing picture originate from New Physics, a modified electroweak penguin sector provides a key scenario. It includes models with extra $Z^{\mathrm{\prime }}$ bosons, which offer attractive ways to resolve anomalies in $B\to K^{(\ast )}{\mathrm{\ell }}^{+}{\mathrm{\ell }}^{-}$ measurements. We present a new strategy to reveal the underlying physics, apply it to current $B\to \pi K$ data, and discuss the excellent prospects for Belle II.