An investigation of the absolute intensity of muons at sea-level

• Published in: Nuclear physics. B 1972-04, Vol.39, p.493-508
• Main Authors: Crookes, J.N., Rastin, B.C.
• Format: Article
• Language: English
• ISSN: 0550-3213; 1873-1562
• DOI: 10.1016/0550-3213(72)90384-7

The absolute intensity of muons at sea-level has been measured using a telescope consisting of two arrays of crossed neon flash tube detectors triggered by a four-fold Geiger counter coincidence. The use of the flash tube information to delineate the particle trajectory has enabled the acceptance solid angle to be defined with an error of only 0.5%. All particles accepted by the telescope were required to penetrate a 10.3 cm thickness of lead which eliminated the soft component and ensured that only muons were detected. The total thickness of absorber penetrated by the triggering particle including all the material of the apparatus as well as that above the experimental site was 184.7 g cm −2 of lead which corresponded to a lower momentum cut-off of 0.35 GeV/ c. These intensity measurements have been made with the axial direction of the telescope in the magnetic NS azimuth for zenith angles of 0°, 45°, 60° and 80°. A comparison with the universally accepted value of the vertical absolute intensity for muons at sea-level given by Rossi from the work of Greisen is included and this shows that the present result (9.13 ± 0.12) × 10 −3 cm −2 s −1 sr −1) is higher by 9%. General agreement with this conclusion is provided by Allkofer et al. although the latter authors claim the Greisen result to be too low by some 26%. A tentative comparison between the present result and that obtained by Allkofer et al. is also given although due to the difference in the lower momentum cut-offs associated with the two instruments use has to be made of the integral spectrum measured by Allkofer and Clausen, the accuracy of which allows only qualitative agreement to be claimed. The variation of absolute intensity with zenith angle obtained in this work has been shown to be adequately represented by the expression I Θ = 9.13 × 10 −3 cos 2.16 Θ for angles less than 75°. Since no other absolute intensity measurements have been performed for zenith angles in the range 0° to 85° a comparison is made of the exponent and this indicates the existence of good agreement between the results from the various workers. The data at large zenith angles has been analysed separately and this is presented together with the work of Jakeman and Wilson.