Measurement ofe+e−→π+π−ψ(2S)via initial state radiation at Belle

We report measurement of the cross section of $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\psi (2S)$ between 4.0 and 5.5 GeV, based on an analysis of initial state radiation events in a $980{\mathrm{fb}}^{-1}$ data sample recorded with the Belle detector. The properties of the $Y(4360)$ and $Y(4660)$ states are determined. Fitting the mass spectrum of ${\pi }^{+}{\pi }^{-}\psi (2S)$ with two coherent Breit-Wigner functions, we find two solutions with identical mass and width but different couplings to electron-positron pairs: $M_{Y(4360)}=(4347\pm 6\pm 3)\mathrm{MeV}/c^2$, ${\mathrm{\Gamma }}_{Y(4360)}=(103\pm 9\pm 5)\mathrm{MeV}$, $M_{Y(4660)}=(4652\pm 10\pm 8)\mathrm{MeV}/c^2$, ${\mathrm{\Gamma }}_{Y(4660)}=(68\pm 11\pm 1)\mathrm{MeV}$; and $\mathcal{B}[Y(4360)\to {\pi }^{+}{\pi }^{-}\psi (2S)]·{\mathrm{\Gamma }}_{Y(4360)}^{e^{+}{e}^{-}}=(10.9\pm 0.6\pm 0.7)\mathrm{eV}$ and $\mathcal{B}[Y(4660)\to {\pi }^{+}{\pi }^{-}\psi (2S)]·{\mathrm{\Gamma }}_{Y(4660)}^{e^{+}{e}^{-}}=(8.1\pm 1.1\pm 0.5)\mathrm{eV}$ for one solution; or $\mathcal{B}[Y(4360)\to {\pi }^{+}{\pi }^{-}\psi (2S)]·{\mathrm{\Gamma }}_{Y(4360)}^{e^{+}{e}^{-}}=(9.2\pm 0.6\pm 0.6)\mathrm{eV}$ and $\mathcal{B}[Y(4660)\to {\pi }^{+}{\pi }^{-}\psi (2S)]·{\mathrm{\Gamma }}_{Y(4660)}^{e^{+}{e}^{-}}=(2.0\pm 0.3\pm 0.2)\mathrm{eV}$ for the other. Here, the first errors are statistical and the second systematic. Evidence for a charged charmoniumlike structure at $4.05\mathrm{GeV}/c^2$ is observed in the ${\pi }^{\pm }\psi (2S)$ intermediate state in the $Y(4360)$ decays.