Search for missing $ψ(4S)$ in the $e^+e^-\to π^+π^-ψ(2S)$ process

A detailed analysis to find a missing $ψ(4S)$ is made by utilizing the recent precise mesurements of the cross section for the process $e^+e^-\to ψ(2S)π^+π^-$ by Belle. Assuming three resonances $Y(4360)$, $Y(4660)$, and $ψ(4S)$ to fit the data, we obtain the resonance parameters for $ψ(4S)$ as $m=4243$ MeV and $Γ=16 \pm 31$ MeV showing a narrow state as predicted before. A combined fit to the data $e^+ e^- \to ψ(2S) π^+ π^-, \ h_c π^+ π^-$, and $χ_{c0} ω$ is also performed to obtain the similar resonance parameters of $ψ(4S)$. The upper limit of the branching ratio is fitted to be $\mathcal{B}(ψ(4S)\toψ(2S)π^+π^-) < 3\times 10^{-3}$, which can be understood by hadronic loop contributions in reasonable parameters range. In addition, the ratios of the branching ratios of the $ψ(4S)$ dipion transition to the one of $ψ(4S)\toχ_{c0}ω$ are fitted, which can be further measured by BESIII and forthcoming BelleII to confirm the existence of $ψ(4S)$.

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