Search for $\psi(4S)\to\eta J/\psi$ in $B^\pm \ra \eta J/\psi K^\pm$ and $e^+ e^- \to \eta J/\psi$ processes

TL;DR

This study searches for the $ ext{psi}(4S)$ state decaying into $ ext{eta} J/ ext{psi}$ in specific B meson and electron-positron collision processes, setting upper limits on its production and decay rates.

Contribution

First search for $ ext{psi}(4S) o ext{eta} J/ ext{psi}$ in these processes, providing experimental upper limits consistent with theoretical predictions.

Findings

No significant $ ext{psi}(4S)$ signal observed.

Upper limit on product branching fraction: $6.8 imes 10^{-6}$.

Branching fraction limit: $<1.3\\%$ at 90\% CL.

Abstract

We search for the $\psi(4S)$ state in $B^\pm \ra \eta J/\psi K^\pm$ and $e^+e^- \ra \eta J/\psi$ based on the Belle measurements with the assumed mass $M=(4230\pm8)$ MeV/$c^2$ and width $\Gamma=(38\pm12)$ MeV. No significant signal is observed in the $\eta J/\psi$ mass spectra. The 90\% confidence level upper limit on the product branching fraction $\BR(B^\pm \ra \psi(4S)K^\pm)\BR(\psi(4S) \ra \eta J/\psi)<6.8\times 10^{-6}$ is obtained in $B^\pm \ra \eta J/\psi K^\pm$ decays. By assuming the partial width of $\psi(4S) \to e^+e^-$ being 0.63 keV, the branching fraction limit $\BR(\psi(4S) \ra \eta J/\psi) < 1.3\%$ is obtained at the 90\% confidence level in $e^+e^- \ra \eta J/\psi$, which is consistent with the theoretical prediction.