An interesting feature of BESIII data for J/Psi -> gamma-(etaprime-pi-pi)

TL;DR

This paper analyzes BESIII data on J/Psi decays, confirming eta(1835) as a pseudoscalar and explaining the absence of eta(1440) in eta'-pi-pi channels through a two-step process involving kaon interactions.

Contribution

It provides a novel explanation for the absence of eta(1440) in eta'-pi-pi decays by proposing a two-step process involving kaon interactions and the Adler zero effect.

Findings

eta(1835) confirmed as a pseudoscalar

Absence of eta(1440) in eta'-pi-pi explained by two-step process

The proposed mechanism accounts for observed decay patterns

Abstract

The eta(1835) is confirmed clearly in new BESIII data for J/Psi -> gamma (eta'-pi-pi); the angular distribution of the photon is consistent with a pseudoscalar. This makes it a candidate for an s-sbar radial excitation of eta' and eta(1440) (or one or both of eta(1405) and eta(1475)). However, a conspicuous feature of the BES III data is the absence of evidence for eta(1440) -> eta'-pi-pi while it is well known that eta(1440) appears in eta-pi-pi. Can these facts be reconciled? There is in fact a simple explanation. The channel eta(1440) -> eta-pi-pi may be explained by the two-step process eta(1440) -> [K*K]_{L=1} and [kappa K ]_{L=0}, followed by KK -> a0(980) -> eta-pi. This process does not produce any significant eta'-pi signal because of the Adler zero close to the eta'-pi threshold.