Study of $f_1(1420)$ and $\eta(1405)$ in the decay $J/\psi \to \gamma \pi^{0}\pi^{0}\pi^{0}$

TL;DR

This study performs a partial-wave analysis of $J/\psi$ decays to three neutral pions, revealing isospin-violating decays of $\eta(1405)$ and $f_1(1420)$, and first-time observations of three axial-vector decays into this final state.

Contribution

It provides the first observation of three axial-vector mesons decaying into three neutral pions and reports their product branching fractions, advancing understanding of meson decay dynamics.

Findings

Isospin-violating decays of $\eta(1405)$ and $f_1(1420)$ observed.

First detection of $f_1(1285)$, $f_1(1420)$, and $f_1(1510)$ decaying into $\pi^{0}\pi^{0}\pi^{0}$.

Product branching fractions of these decays are measured.

Abstract

A partial-wave analysis is performed on the decay $J/\psi\to\gamma\pi^{0}\pi^{0}\pi^{0}$ within the $\pi^{0}\pi^{0}\pi^{0}$ invariant-mass region below 1.6 GeV$/c^{2}$, using $(10.09~\pm~0.04)\times10^{9} ~J/\psi$ events collected with the BESIII detector. Significant isospin-violating decays of $\eta(1405)$ and $f_1(1420)$ into $f_0(980)\pi^{0}$ are observed. For the first time, three axial-vectors, $f_1(1285)$, $f_1(1420)$ and $f_1(1510)$, are observed to decay into $\pi^{0}\pi^{0}\pi^{0}$. The product branching fractions of these resonances are reported.