Cross section measurement of $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\psi (3686)$ from $\sqrt{s}=4.0076\mathrm{GeV}$ to 4.6984 GeV

Using data samples with a total integrated luminosity of $20.1{\mathrm{fb}}^{-1}$ collected by the BESIII detector operating at the BEPCII collider, the cross section of the process $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\psi (3686)$ is measured at center-of-mass energies between 4.0076 and 4.6984 GeV. The measured cross section is consistent with previous results, and with much improved precision. A fit to the measured energy-dependent cross section, which includes three Breit-Wigner functions and a nonresonant contribution, confirms the existence of the charmonium-like states $Y(4220)$, $Y(4390)$, and $Y(4660)$. This is the first observation of the $Y(4660)$ at the BESIII experiment.

Figure 1

Distributions of $M(l^{+}{l}^{-})$ for Mode I (a) after the 4C (1C) kinematic fit and Mode II (b) after applying the selection criteria for the data sample with c.m. energy at 4.3583 GeV. Dots with error bars are data, the blue curve is for signal MC sample, the closed red arrows indicate the signal regions, and the open green arrows indicate the sideband regions.

Figure 2

Distributions of $M(l^{+}{l}^{-}{\pi }^{+}{\pi }^{-})$ for Mode I (a) and $M^{\mathrm{rec}}({\pi }^{+}{\pi }^{-})$ for Mode II (b) for data with a c.m. energy of 4.3583 GeV. Dots with error bars are data, the shaded histograms represent the background events in the $J/\psi$ sideband regions, the solid curves are the fit results, and the dashed curves are the background contributions from the fit.

Figure 3

Comparison of the cross section among this work, previous work of BESIII [16], Belle [14] and BABAR [15]. The open circles represent the results of this work. The full triangles are from previous BESIII work. The open squares are from BABAR work. The full squares are from Belle work.

Figure 4

The dressed cross section fit results of the process $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\psi (3686)$ corresponding to the four solutions in Table 3. The black dots with error bars are the measured dressed cross section, the blue solid curves are the best-fit results, the red dashed lines represent individual resonant structures, the green dotted lines show the continuous component, and the gray dot-dashed lines are the sum of all interference terms. The bottom panel in each plot is the $\chi$ distribution.

Figure 5

(a) Masses versus widths of the $Y(4220)$ and $Y(4390)$ obtained from different processes in BESIII [7, 8, 9, 10, 11, 12]. (b) Masses versus widths of resonances observed in $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\psi (3686)$ from this work and other experiments [14, 15].