MEASUREMENT OF THE ATMOSPHERIC MUON NEUTRINO FLUX WITH THE MACRO DETECTOR

The flux of muon neutrinos in the 1 - 1000 GeV range has been measured with the MACRO underground detector. The measurement has been perform ed by means of the time-of-flight method to separate upward-going muon s coming from neutrino interactions in the surrounding rock from downw ard-going muons coming directly from cosmic ray cascades. The analysis results for data collected since March 1989 up to November 1996 are s ummarized. The zenith angular dependence of the measured upward-going muon flux is compared with the expected one assuming the Bartol atmosp heric neutrino flux. Also upward-going muons generated inside the dete ctor have been detected.