# Measurement of Branching Fractions of $\psi(3686)\rightarrow\phi\eta^\prime, \phi f_1(1285)$ and $\phi \eta(1405)$

## TL;DR

This study measures branching fractions of $\psi(3686)$ decays into various $\phi$ and meson states with improved precision, observing significant resonances and providing new detailed decay data.

## Contribution

The paper provides the first precise measurements of branching fractions for $\psi(3686)$ decays into $\phi ext{ and meson}$ states, including clear observation of $f_1(1285)$ and $\eta(1405)$ resonances.

## Key findings

- Branching fraction of $\psi(3686)
ightarrow\phi ext{ }\eta^ extprime$ measured as $(1.51\pm0.16\pm0.12) imes 10^{-5}$.
- Resonances $f_1(1285)$ and $\eta(1405)$ observed with high significance in the $\pi^{+}\pi^{-}\eta$ spectrum.
- Product branching fractions for $\psi(3686)$ decays into these resonances are quantified.

## Abstract

Using a sample of $448.1\times10^6$ $\psi(3686)$ events collected with the BESIII detector, we perform a study of the decay $\psi(3686) \rightarrow \phi \pi^{+}\pi^{-}\eta$. The branching fraction of $\psi(3686)\rightarrow\phi\eta^\prime$ is determined to be $(1.51\pm0.16\pm0.12)\times 10^{-5}$, which is consistent with the previous measurement but with significantly improved precision. The resonances $f_{1}(1285)$ and $\eta(1405)$ are clearly observed in the $\pi^{+}\pi^{-}\eta$ mass spectrum with statistical significances of $18\sigma$ and $9.7\sigma$, respectively. The corresponding product branching fractions are measured to be $\mathcal{B}(\psi(3686)\rightarrow\phi f_{1}(1285),f_{1}(1285)\rightarrow\pi^{+}\pi^{-}\eta) =(1.03\pm0.10\pm0.09)\times 10^{-5}$ and $\mathcal{B}(\psi(3686)\rightarrow\phi\eta(1405),\eta(1405)\rightarrow\pi^{+}\pi^{-}\eta) =(8.46\pm1.37\pm0.92)\times 10^{-6}$.