An analysis of the structure in the M$_{\mu\pi}$ spectra from the K$_{L}^{0}$ decay

The physical structure in the M/sub mu pi / spectra from the K/sup 0 //sub L/, attributed to the existence of neutral heavy leptons has been analysed in a Dalitz plot of data from a spark chamber experiment which accepts all configurations of the kaon decays. The results are compatible with the existence of a neutral heavy lepton with the previously observed mass: M*/sub mu pi /(429)=(0.429+or-0.002) GeV. There is also a compatibility between the angular distributions associated with the M*/sub mu pi / in these data and those observed in other spark chamber experiments which do not accept all laboratory configurations of the kaon decays. (9 refs).