Analysis of discrepancies in Dalitz plot parameters in η → 3pi decayI

We analyze the Dalitz plot parameters of η→3pi decay in the framework of resummed chiral perturbation theory. This approach allows us to keep the uncertainties in the NNLO and higher orders under better control and estimate their influence. We cannot confirm the suspected discrepancy in the case of the charged decay parameter b, where even small uncertainties in higher orders could accommodate the difference. On the other hand, we find the experimental value of the neutral decay parameter α incompatible with an assumption of good convergence properties in the center of the Dalitz plot. We calculate pipi rescattering bubble corrections up to three loops and show that these might explain the discrepancy, especially for a low value of the pseudoscalar decay constant in the chiral limit. However, that could indicate a failure of convergence of the chiral series in this channel already at low energies around 500MeV. Keywords: chiral perturbation theory, eta meson, pipi rescattering Chiral perturbation theory [1, 2] has a long history [3] of trying to explain experimental data on the η→3pi decay. As is clear from the decay rate calculations, the theory converges really slowly for this decay channel