Search for long-lived neutral resonances in Bhabha scattering around 1.8 MeV/c2
Date
1990Source
Physical Review LettersVolume
65Issue
8Pages
972-975Google Scholar check
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A search has been carried out for long-lived neutral particles which could be created in resonant e+e- scattering, with an invariant mass around 1.8 MeV/c2. A monoenergetic positron beam was scattered from a thin Be foil, and an active-shadow technique was used to suppress elastic e+e- scattering. No evidence was found for neutral particles decaying dominantly into e+e- pairs, in the lifetime region between 4.5×10-13 and 7.5×10-12 s (95% C.L.). This result, together with our previous work, eliminates recent theoretical models that have introduced new neutral particles in this mass region. © 1990 The American Physical Society.