A STUDY OF UNDERGROUND COSMIC-RAY MUON INTENSITIES AT VERY LARGE ZENITH ANGLES
Underground cosmic-ray muon intensities were investigated at zenith angles from 71 to 89- for oblique depths from 82 meters of water equivalent to 362 meters of water equivalent of rock. The investigation was made near sea level with a hodoscope-telescope, and the absolute intensities were measured in an underground limestone quarry' behind a smooth vertical bluff. From the data, the sealevel energy spectra were inferred for energies between 15 and 90 Bev. The slopes of the energy spectra at fixed zenith angle were found to increase with energy, reflecting the increasing atmospheric absorption loss of parent pions as their mean lifetimes increased with energy. In addition the slopes were found to decrease with increasing zenith angle at fixed energy, reflecting the decreasing loss of pions at high altitudes by absorption as the average density of air per unit of path length decreased. The zenithal dependence of the sea- level muon intensity was also inferred at fixed energies from 20 to 90 Bev for angles between 70 and 90 deg . The experimental results are shown to be in good agreement with theoretical predictions of others at angles near 70 deg . Discrepancies observed at higher angles are explained in terms of the flat- atmosphere approximation used in the theory. The resuits suggest a pi-meson absorption mean-free-path between 60 and 120 g/cm/sup 2/, with no evidence for a value above 120 g/cm2. The exponent of the differential pi-meson production spectrum was determined to be 2.66 plus or minus 0.06, and it is shown to be independent of zenith angle and energy in the intervals investigated.
- Research Organization:
- Univ. of Missouri, Columbia
- NSA Number:
- NSA-16-033662
- OSTI ID:
- 4780060
- Journal Information:
- Dissertation Abstr., Vol. Vol: 23; Other Information: Orig. Receipt Date: 31-DEC-62
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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