The orthopositronium decay puzzle and primordial nucleosynthesis

The discrepancy between the experimental decay rate of orthopositronium (o-Ps) and the QED theoretical prediction can be solved by invoking decays of o-Ps into exotic particles with branching ratios ∼ 10−3. We show that considerations based on primordial nucleosynthesis and effective Lagrangians place a very stringent upper bound: B ≡ Γ(o-Ps → “exotic” + …)Γ(o-Ps) ≤ 2 × 10−15, ruling out the exotic decay solution to the puzzle.