Measurement of the branching fraction of the decay $J/\psi \to p \bar{p} \eta$

TL;DR

This paper reports a high-precision measurement of the branching fraction of the decay $J/ar{J} o p ar{p} \eta$ using a large dataset from BESIII, including separate measurements for different $\eta$ decay modes and a combined result, with no observed threshold enhancement.

Contribution

The study provides the most precise measurement to date of the $J/ar{J} o p ar{p} \\eta$ branching fraction, including analysis of $\\eta$ decay modes and threshold region investigation.

Findings

Branching fraction of $J/\psi \to p \bar{p} \eta$ is $(1.495 \pm 0.001 \pm 0.023) \times 10^{-3}$.

No evidence of threshold enhancement in the $p \bar{p}$ invariant mass spectrum.

Measurements are compatible with previous results within uncertainties.

Abstract

A high precision measurement of the branching fraction of the decay $J/\psi \to p \bar{p} \eta$ is performed using $(10 087 \pm 44) \times 10^6$ $J/\psi$ events recorded by the {BESIII} detector at the {BEPCII} storage ring. The branching fractions of the two decays $J/\psi \to p \bar{p} \eta(\eta \to \gamma\gamma)$ and $J/\psi \to p \bar{p} \eta(\eta \to \pi^+ \pi^- \pi^0)$ are measured individually to be $\mathcal{B}(J/\psi \to p \bar{p} \eta(\eta \to \gamma\gamma)) = (1.480 \pm 0.001 \pm 0.024)\times\,10^{-3}$ and $\mathcal{B}(J/\psi \to p \bar{p} \eta(\eta \to \pi^+ \pi^- \pi^0)) = (1.557 \pm 0.003 \pm 0.038)\times\,10^{-3}$, where the first uncertainties are statistical and the second systematic. Both results are compatible within their uncorrelated systematic uncertainties. The combined result is $\mathcal{B}(J/\psi \to p \bar{p} \eta)=(1.495 \pm 0.001 \pm 0.023)\times\,10^{-3}$ where the first uncertainty is the combined statistical uncertainty and the second one the combined systematic uncertainty of both analyses, incorporating correlations between them. In addition, the $p \bar{p}$ threshold region is investigated for a potential threshold enhancement, and no evidence for one is observed.