Lessons from LHCb and Belle II measurements of $B\to J\mathrm{/}\psi \pi$ and $B\to J\mathrm{/}\psi K$ decays

The LHCb collaboration has recently measured the CP asymmetry in $B^{+}\to J\mathrm{/}\psi {\pi }^{+}$ decay, while the Belle II collaboration has recently measured the CP asymmetries in $B^0\to J\mathrm{/}\psi {\pi }^0$ decay. Within the Standard Model, and using flavor-$SU(3)$ relations including first-order breaking corrections, these measurements lead to new predictions with regard to CP violation in $B^{+}\to J\mathrm{/}\psi K^{+}$ and $B_s\to J\mathrm{/}\psi \bar{K}{}^0$ decays, the difference between $S_{\psi K_S}$ and $\sin 2\beta$, and the rate and CP asymmetries in $B_s\to J\mathrm{/}\psi {\pi }^0$ decay.