CERN Accelerating science

The $K^{0}\to4μ$ decays are very suppressed in the Standard Model, with expected branching fractions at the level of $10^{-14}$ for the short-living kaon ($K_S^{0}$) and $10^{-13}$ for the long-lived kaon ($K_L^{0}$). Those branching fractions can be enhanced by mediators from Dark Sector models and become potentially detectable by the LHCb experiment with its Run-II dataset, especially via the decays of the short-living $K^{0}$ meson ($K_S^{0}$). A search for the decays $K_S^{0}→μ^+μ^-μ^+μ^-$ is performed using 5.1 fb^{-1} of pp collisions detected by the LHCb experiment during the Run II of the Large Hadron Collider.