THE θ-τ PUZZLE REVISITED

After Dalitz¹ deduced from a detailed analysis of experimental data that the decay products of the apparently "like" mesons θ and τ, into 2π and 3π, respectively, form states of opposite parity, attempts were made to find differences in some of the properties of θ and τ before decay, by measuring the mass, lifetime, and scattering for each. Within the accuracy attained no differences were found, but from such experiments a definitive proof of identity cannot be reached, even with "asymptotically" improved acuracy. Since identity would have implied the nonconservation of parity, contradicting an important symmetry principle, thus the θ-τ puzzle was born!...

Note from Publisher: This article contains the abstract and references only.