Zenith - Angle Distribution of J

March 197-i ABSTR.ACT The flux of atmospheric muons as a function of momentum and zenith angle is measured for p > 0.3 TeV and 60" < 8 C 87.. Special attention is given the angular distribution above. 1 TeV. In 1967, Bergeson et al. [i] published data from an underground cosmic ray experiment, suggesting that a new process is occurring in nucleon-nudleon interactions at energies of several TeV. They observed the angular distribution of muons penetrating to great , depths'underground , and instead of finding the enhancement at large I zenith angles'ihat is expected if.&ns are produced by the decay of. pions and kaons, they saw an isotropic distribution. The simplest interpretation of these results was that a substantial fraction'of muons above 1 TeV are produced directly or via a very short-lived parent, since it is the intermediate long-lived parents (pions and kaons) in the conventional model that give the enhancement at large zenith angles, owing to the competition between interaction .and decay in the upper atmosphere. Subsequent results from the same group [Z] indicated that the fraction of directly produced muons is much smaller than the original paper had suggested. An underground experiment from the Kolar gold fields 133 has disagreed with the Utah results. The contribution of magnetic spectrometers to this question has been mainly at energies below those corresponding to the Utah experiment's depths. No anomalies have been seen at 0.3 TeV [4] and up'to 1 TeV [5]. Both criticism and support of the Utah results have ,been based on indirect relationships to other cosmic-ray experiments; for a general survey of experiments up to November 1970, see refs. [6] and [7]. It is .clear that such a new process would have great impact on particle physics. A discussion of some of the implications of anomalous muon production is given by Bjorken et al. [S] .-2-In an effort to avoid the uncertainties in an underground experiment caused by the passage of muons through large amounts of rock, we have performed a magnetic spectrometer experiment at sea level, with optical spark chambers and an air-gap magnet. .Our experiment was set up in the experimental yard at the Staliford Linear Accelerator r Center. Since the expected ,enhancement from the .conventional mod,el increases with zenith angle; our experiment covers large zenith th angles (6) from 60 " to 87') with a-total geometry factor of 570 2 cm-sr. We report here on …