Lessons from LHCb and Belle II measurements of $B\to J/ψπ$ and $B\to J/ψK$ decays

Abstract

The LHCb collaboration has recently measured the CP asymmetry in $B^+\to J/ψπ^+$ decay, while the Belle II collaboration has recently measured the CP asymmetries in $B^0\to J/ψπ^0$ 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 $B^+\to J/ψK^+$ and $B_s\to J/ψ\overline{K}{}^0$ decays, the difference between $S_{ψK_S}$ and $\sin2β$, and the rate and CP asymmetries in $B_s\to J/ψπ^0$ decay.