Near muon range detector for the K2K experiment: Construction and performance

A muonrange detector (MRD) has been constructed as a near detector for the KEK-to-Kamioka long-baseline neutrinoexperiment (K2K). It monitors the neutrinobeam properties at the near site by measuring the energy, angle and production point of muonsproduced by charged-current neutrinointeraction. The detector has been working stably since the start of the K2K experiment.