Abstrakt
The convergence of the decay widths and some of the Dalitz plot parameters of the decay eta -> 3 pi seems problematic in low energy QCD. In the framework of resummed chiral perturbation theory, we explore the question of compatibility of experimental data with a reasonable convergence of a carefully defined chiral series.
By treating the uncertainties in the higher orders statistically, we numerically generate a large set of theoretical predictions, which are then confronted with experimental information. In the case of the decay widths, the experimental values can be reconstructed for a reasonable range of the free parameters and thus no tension is observed, in spite of what some of the traditional calculations suggest.
The Dalitz plot parameters a and d can be described very well too. When the parameters b and alpha are concerned, we find a mild tension for the whole range of the free parameters, at less than 2 sigma C.L.
This can be interpreted in two ways - either some of the higher order corrections are indeed unexpectedly large or there is a specific configuration of the remainders, which is, however, not completely improbable.