Unexplained Structure in (mu,pi) Invariant Mass Distributions

Abstract

Structures in invariant mass distributions from (mu,pi) combinations in the range 0.380<mupi<0.470 GeV from neutrino and kaon experiments are presented in comparable formats. No artifacts have been found to account for any part of the structure. Hypotheses that the similarities are due to recurrent statistical fluctuations are beyond credibility. My conclusion is that the similarities are overwhelming evidence that the structure is of an unexplained physical origin. It includes an enhancement which would accord with the decay of a narrow (mu,pi) state of mass 0.429 GeV. The purpose of this report is to request and enable every experimenter with precise mupi distributions to investigate their degree of correspondence with these analyses.