The positron peak puzzle - recent results from APEX
- and others
Results are presented from a new experiment, APEX, designed to study the previously reported sharp lines in sum-energy spectra of positrons and electrons produced in collisions of very heavy ions. Data have been collected for {sup 238}U+{sup 181}Ta and {sup 238}U+{sup 232}Th. No evidence is found for narrow structures similar to those previously reported. For the specific case of the isolated decay of a neutral particle of mass 1.4-2.1 MeV/c{sup 2}, the upper limits on cross sections obtained are significantly less than previously reported. Data are also presented for internal pair conversion in {sup 206}Pb. These results are used to set limits for the possible contribution to the pair yield of a 1780 keV transition in {sup 238}U observed in heavy-ion gamma-ray coincidence measurements.
- Research Organization:
- Argonne National Lab., IL (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 196563
- Report Number(s):
- ANL/PHY/CP--88465; CONF-9508181--2; ON: DE96004170
- Country of Publication:
- United States
- Language:
- English
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