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Journal Articles Physics Letters B Year : 2002

Search for an exotic three-body decay of orthopositronium

A. Badertscher
  • Function : Author
P. Crivelli
  • Function : Author
M. Felcini
  • Function : Author
S.N. Gninenko
  • Function : Author
N.A. Goloubev
  • Function : Author
V. Postoev
  • Function : Author
A. Rubbia
  • Function : Author


We report on a direct search for a three-body decay of the orthopositronium into a photon and two penetrating particles, o-Ps -> gamma + X1 + X2. The existence of this decay could explain the discrepancy between the measured and the predicted values of the orthopositronium decay rate. From the analysis of the collected data a single candidate event is found, consistent with the expected background. This allows to set an upper limit on the branching ratio < 4.4 \times 10^{-5} (at the 90% confidence level), for the photon energy in the range from 40 keV < E_gamma< 400 keV and for mass values in the kinematical range 0 < mX1+mX2 <900 keV. This result unambiguously excludes the o-Ps -> gamma + X1 + X2 decay mode as the origin of the discrepancy.

Dates and versions

in2p3-00019966 , version 1 (25-11-2002)



A. Badertscher, P. Crivelli, M. Felcini, S.N. Gninenko, N.A. Goloubev, et al.. Search for an exotic three-body decay of orthopositronium. Physics Letters B, 2002, 542, pp.29-34. ⟨in2p3-00019966⟩
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