Study of $\eta(1405)/\eta(1475)$ in $J/\psi\to\gamma K^{0}_{S} K^{0}_{S}\pi^{0}$ decay

TL;DR

This study performs a detailed partial wave analysis of $J/ar{J}$ decays to identify and characterize the $ ext{η}(1405)$ and $ ext{η}(1475)$ resonances, providing precise measurements of their masses and widths.

Contribution

It introduces a comprehensive analysis using covariant tensor amplitudes to distinguish between the $ ext{η}(1405)$ and $ ext{η}(1475)$ resonances in $J/ar{J}$ decays, with improved parameter measurements.

Findings

Identified two isoscalar resonant states: $ ext{η}(1405)$ and $ ext{η}(1475)$.

Measured the masses and widths of both resonances with statistical and systematic uncertainties.

Confirmed the dominance of pseudoscalar and axial vector components in the decay spectrum.

Abstract

Using a sample of $(10.09\pm0.04)\times10^{9}$ $J/\psi$ decays collected with the BESIII detector, partial wave analyses of the decay $J/\psi\to\gamma K^{0}_{S} K^{0}_{S}\pi^{0}$ are performed within the $K^{0}_{S}K^{0}_{S}\pi^{0}$ invariant mass region below $1.6\mathrm{\ Ge\kern -0.1em V}/c^2$. The covariant tensor amplitude method is used in both mass independent and mass dependent approaches. Both analysis approaches exhibit dominant pseudoscalar and axial vector components, and show good consistency for the other individual components. Furthermore, the mass dependent analysis reveals that the $K^{0}_{S}K^{0}_{S}\pi^{0}$ invariant mass spectrum for the pseudoscalar component can be well described with two isoscalar resonant states using relativistic Breit-Wigner model, ${\it i.e.}$, the $\eta(1405)$ with a mass of $1391.7\pm0.7_{-0.3}^{+11.3}\mathrm{\ Me\kern -0.1em V}/c^2$ and a width of $60.8\pm1.2_{-12.0}^{+5.5}\mathrm{\ Me\kern -0.1em V}$, and the $\eta(1475)$ with a mass of $1507.6\pm1.6_{-32.2}^{+15.5}\mathrm{\ Me\kern -0.1em V}/c^2$ and a width of $115.8\pm2.4_{-10.9}^{+14.8}\mathrm{\ Me\kern -0.1em V}$. The first and second uncertainties are statistical and systematic, respectively. Alternate models for the pseudoscalar component are also tested, but the description of the $K^{0}_{S}K^{0}_{S}\pi^{0}$ invariant mass spectrum deteriorates significantly.