Limit on an exotic three-body decay of orthopositronium

T. Mitsui, K. Maki, S. Asai, Y. Ishisaki, R. Fujimoto, N. Muramoto, T. Sato, Y. Ueda, Y. Yamazaki, S. Orito

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16 Citations (Scopus)


An exotic annihilation of e+e- at rest into a single γ and a weakly interacting neutral vector boson V0 was searched for by measuring the related γ energy under the condition that no additional γ was detected by a hermetic detector. No evidence of such an annihilation was observed, resulting in the upper limits on the branching ratio of 4.2 × 10-6 (mvo < 200 keV/c2) and 2.1 × 10-5 (mvo < 2me = 1022 keV/c2). These upper limits were converted to those on the branching ratio of an exotic three-body decay (γγV0) of orthopositronium (o-Ps), i.e. 6.2 × 10-6 (mvo < 200 keV/c2) and 1.7 × 10-5 (mvo < 2me). As a result, this mode was definitely excluded as the source of the reported discrepancy in the o-Ps decay rate.

Original languageEnglish
Pages (from-to)111-116
Number of pages6
JournalEurophysics Letters
Issue number2
Publication statusPublished - 1996 Jan 10
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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