The branching fraction of $$ {B}_s^0\to {K}^0{\overline{K}}^0 $$: three puzzles

A bstract The branching fraction of the $$ {B}_s\to {K}^0{\overline{K}}^0 B s → K 0 ¯ decay has been recently measured by LHCb and Belle experiments. We study consistency value with three relations to other rates CP asymmetries which follow from Standard Model, approximate flavor SU(3) symmetry strong interactions. find that each these is violated at a level above 3 σ . argue various subleading effects — rescattering, electroweak penguins breaking if larger than theoretically expected, can account for some puzzles, but not all them simultaneously.