New limits on exotic two-body decay of orthopositronium
1989; American Physical Society; Volume: 63; Issue: 6 Linguagem: Inglês
10.1103/physrevlett.63.597
ISSN1092-0145
AutoresS. Orito, Kotaro Yoshimura, Takeshi Haga, M. Minowa, M. Tsuchiaki,
Tópico(s)Nuclear physics research studies
ResumoMotivated by the recently reported discrepancy between measured and theoretical values for the orthopositronium lifetime, we have searched for exotic decay of orthopositronium into \ensuremath{\gamma} plus a long-lived neutral particle X, in the hitherto unexplored mass region of ${m}_{x}$ below 100 keV. Our negative result provides new upper limits of 6.4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$ to 7.6\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}6}$ 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.
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