IS THERE A NEW PSEUDOSCALAR PARTICLE?

The decay rate of orthopositronium has recently been measured in a new high precision experiment. The result is 10 standard deviations above the theoretical value. It is shown that a light neutral pseudoscalar R may resolve this discrepancy and still be consistent with the anomalous magnetic moments of the electron and the muon. If the mass mR≤5.7 keV , then the existence of this proposed particle R is consistent with the beam-dump experiments. The lifetime of R is large, τ≥0.14 s.