Cosmic ray muon measurement by the L3 spectrometer at CERN

L3+C is a branch experiment on L3 magnet spectrometer, which is located on the ring of LEP accelerator at CERN. To take the advantage of L3 muon chambers in its low threshold, wide dynamic range and high resolution, the momentum of cosmic ray muons in the range of 15-2000 GeV/c at a shallow depth of 30 m of molasse can be measured precisely. Since 1998, a scintillator detector system, a new fast trigger and DAQ system, and a small air shower array had been established for study the CR muon events independently. Up to August 2000, 8 billion muons and 25 million air shower events had been recorded. The first results for CR muon spectrum and the charge ratio etc. had been obtained. (3 refs).