# Search for the rare decay $\eta'\rightarrow\pi^{0}\pi^{0}\pi^{0}\pi^{0}$ at BESIII

## TL;DR

This study searches for the rare decay of eta prime into four neutral pions using BESIII data, setting a new upper limit on its branching fraction, which improves previous constraints significantly.

## Contribution

First search for eta' to 4 pi0 decay at BESIII, establishing a more stringent upper limit on its branching fraction.

## Key findings

- No significant signal observed for eta' to 4 pi0 decay.
- Upper limit on branching fraction set at 4.94×10⁻⁵ with 90% confidence.
- Result is six times more restrictive than previous experimental limits.

## Abstract

Based on a sample of 1.31 billion $J/\psi$ events collected with the BESIII detector, we perform a search for the rare decay $\eta'\rightarrow 4\pi^{0}$ via $J/\psi\rightarrow\gamma\eta'$. No significant $\eta'$ signal is observed in the invariant mass spectrum of 4$\pi^{0}$. With a Bayesian approach, the upper limit on the branching fraction of $\eta'\rightarrow 4\pi^{0}$ is determined to be $\mathcal{B}(\eta'\rightarrow 4\pi^{0})$ $< 4.94\times10^{-5}$ at the 90\% confidence level, which is a factor of six smaller than the previous experimental limit.