Abstract
Electron-positron angular correlations were measured for the isovector magnetic dipole 17.6 MeV (, ) state (, ) and the isoscalar magnetic dipole 18.15 MeV (, ) state transitions in . Significant enhancement relative to the internal pair creation was observed at large angles in the angular correlation for the isoscalar transition with a confidence level of . This observation could possibly be due to nuclear reaction interference effects or might indicate that, in an intermediate step, a neutral isoscalar particle with a mass of and was created.
- Received 7 April 2015
DOI:https://doi.org/10.1103/PhysRevLett.116.042501
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Published by the American Physical Society