A scintillator based endcap KL and muon detector for the Belle II experiment

A new KL0 and muon detector based on scintillators will be used for the endcap regions in the Belle II experiment, currently under construction. The increased luminosity of the e+e− SuperKEKB collider entails challenging detector requirements. We demonstrate that relatively inexpensive polystyrene scintillator strips with wavelength shifting fibers ensure a sufficient light yield at the Silicon PhotoMultiplier (SiPM) photodetector, are robust and provide improved physics performance for the Belle II experiment compared to its predecessor, Belle.