New limits on exotic two-body decay of orthopositronium

S. Orito, K. Yoshimura, T. Haga, M. Minowa, M. Tsuchiaki

Research output: Contribution to journalArticle

26 Citations (Scopus)


Motivated by the recently reported discrepancy between measured and theoretical values for the orthopositronium lifetime, we have searched for exotic decay of orthopositronium into plus a long-lived neutral particle X, in the hitherto unexplored mass region of mx below 100 keV. Our negative result provides new upper limits of 6.4×10-5 to 7.6×10-6 on the branching ratio of such decay. Consequently we exclude the hypothesis of Samuel, i.e., that a new pseudoscalar particle with mass less than 5.7 keV is responsible for the discrepancy of the orthopositronium lifetime.

Original languageEnglish
Pages (from-to)597-600
Number of pages4
JournalPhysical Review Letters
Issue number6
Publication statusPublished - 1989
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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