Data on J/Psi -> gamma(Kcharged-Kshort-picharged) and gamma(eta-piplus-piminus)

TL;DR

This study analyzes J/Psi decay data to gamma eta pi pi and gamma K charged K short pi charged, providing new insights into J^P=0^- mesons, especially eta(1440), and examining the existence of multiple resonances.

Contribution

It introduces a comprehensive analysis of eta(1440) including full s-dependence of decay channels and challenges the notion of separate eta(1405) and eta(1475) resonances.

Findings

No significant evidence for two separate eta resonances.

Eta(1440) fits well with a single state including s-dependence.

Detection of broad J^P=0^- peak at 1850 MeV and signals for eta2(1870).

Abstract

Data on J/Psi -> gamma (eta-piplus-piminus) and gamma (Kcharged-Kshort-picharged) from 58M J/Psi hadronic interactions in the BES II detector are analysed. They throw new light on J^P = 0^- mesons throughout the mass range up to 2 GeV, notably eta(1440). For the first time, this state is fitted including the full s-dependence of decays to a0(980)-pi, eta-sigma, Kstar-K, kappa-K and f0(980)-eta, including the dispersive term associated with this s-dependence. Two types of fit are reported. The first uses a single eta(1440). The second uses separate eta(1405) and eta(1475). The strong s-dependence of P-wave production of Kstar-K shifts the fitted mass of eta(1475) down to 1440 MeV. As a result, the two types of fit give almost identical results and the conclusion from these data is that there is no significant evidence for two separate resonances. In KKpi, there are definite though small contributions from f1(1420) and f1(1285). The optimum fit requires either a small additional f1(1510) or alternatively a small perturbation to the high mass tail of f1(1420). At higher masses, there is a broad J^P=0^- peak in eta-pi-pi at 1850 MeV. There is also a weak but definite signal consistent with eta2 (1870) -> eta-pi-pi.