Branching fraction measurement of the $B^0\to K^+π^-μ^+μ^-$ decay at high dihadron mass

This Letter presents the first measurement of the $B^{0} \to K^{+}π^{-}μ^{+}μ^{-}$ differential branching fraction in the region of the dihadron $K^+π^-$ mass, $m_{Kπ}$, $1000< m_{Kπ} < 1835\,\text{MeV}/c^{2}$. This decay mode is mediated by the quark-level transition $b \to s\ell^{+}\ell^{-}$, for