Measurement of the branching fraction for the decay $K_S \to \pi \mu \nu$ with the KLOE detector

Understand

Based on a sample of 300 million $K_S$ mesons produced in $\phi \to K_L K_S$ decays recorded by the KLOE experiment at the DA$\Phi$NE $e^+e^-$ collider we have measured the branching fraction for the decay $K_S \to \pi \mu \nu$.

• The $K_S$ mesons are identified by the interaction of $K_L$ mesons in the detector.
• The $K_S \to \pi \mu \nu$ decays are selected by a boosted decision tree built with kinematic variables and by a time-of-flight measurement.
• Signal efficiencies are evaluated with data control samples of $K_L \to \pi \mu \nu$ decays.