Direct Electron Pair Production by High-Energy Muons

Planning of new accelerators and the problems of contemporary elementary-particle physics

“…Kearney and Hazen (1965) operated at a depth of 842 hg cm-2 where the pair production cross section is -5 times higher than knock-on and they found no significant deviation between theory and experiment. The present experiment confirms this result, but with better statistical precision and is in total disagreement with the results of Allhofer et a1 (1972) and Jain (1974).…”

“…The need to update the survey here is not considered vital because only the three more recent experiments of Grupen et al (1972), Binns and Kearney (1972) and Jain et al (1974) are not included in the survey. Furthermore, the investigation of Binns and Kearney was at an intermediate depth of 274 hg cm-2 where the pair production cross section lies below that for knock-on, while the burst experiment of Grupen et a1 is of limited precision.…”

A Reevaluation of Evidence for Light Neutral Bosons in Nuclear Emulsions

“…The events shown in the background-subtracted spectra of Fig. 5, together with one event at 9.8 MeV/c 2 well-separated from background from [13], events at 5.5, 7.0 and 16.5 MeV/c 2 well-separated from background from [4], and an event at 9.5 MeV/c 2 well-separated from background from [5] were added within 1-MeV/c 2 bins; the sum spectrum is shown in Fig. 6.…”

“…For over 50 years, measurements of e + e − pair production by energetic ions incident on emulsion detectors have yielded events with opening angles at the e + − e − vertex larger than those expected [1] for external pair conversion (EPC) by photons [2,3,4,5,6,7,8,9,10,11]. On the basis of relatively small data sets, El-Nadi and Badawy [6] and de Boer and van Dantzig [12] proposed in 1988 that such events might represent the decays of neutral bosons with masses considerably larger than generally expected for Weinberg-Wilczek axions.…”

“…In this paper, we revisit results from six accelerator studies using emulsion detectors, all of which report observations of e + e − pairs that are interpreted as evidence for the existence of neutral bosons with masses between 1.5 and 30 MeV/c 2 and lifetimes between 10 −16 and 10 −14 s [4,5,6,7,8,9,10,11,13]. Four of these studies [9,10,11,13] were published after the 1988 proposal that such events might represent the decays of massive neutral bosons [6,12], and hence can be considered tests of this proposal.…”