M.A.R.S: the charge ratio of muons in the range 20-500 geV/c in the vertical direction

Abstract

The sae level muon charge ratio in the near vertical direction has been measured using the Durham spectrograph M.A.R.S. in the religion 10 GeV/c to about 500 GeV/c. A detailed description of the apparatus used in the experiment is given. Based on approximately 1.3 x 10(^6) particles the mean ratio, over the whole energy range is found to be l.2850 + 0.0023. This is consistent with previous measurements made with the same instrument and also with results of other workers. No evidence for pronounced maxima or minims in the ratio as a function of momentum is seen. There is however, some indication of a broad maximum in the ratio in the region 20-50 GeV/c followed by a somewhat lower ratio to about 200 GeV/c. Using data from the intersecting storage rings experiment an attempt has been made to estimate the expected muon change ratio at sea level. This estimated ratio is found to be higher than the observed value. The reasons for the discrepancy are thought to be a combination of inadequate pion production data and the effects of intranuclear cascading. Other possible causes - a breakdown in scaling and changes in the primary spectrum are also discussed.