OBSERVATION OF ELECTROMAGNETIC-INTERACTIONS OF HIGH-ENERGY MUONS DEEPUNDERGROUND

The first experimental measurement of the spectrum of cascade showers produced by cosmic ray muon interactions deep underground in the trans ferred energy range 0.4-200 GeV has been performed by means of the NUS EX calorimeter at a depth of about 5000 hg/cm(2), the average muon ene rgy being close to 360 GeV. The spectrum of energy transfers is in goo d agreement with calculations based on the commonly used theoretical f ormulas for muon interaction cross sections and on a conservative pict ure of the formation of muon energy spectrum at great depths. The pres ent data do not confirm the deficit of the cross section at low energy transfers for the 1 TeV muon energy recently reported by the CCFR Col laboration. A possible explanation of the difference between the obser ved and the expected stochastic energy loss distributions presented by the CCFR group is discussed.