Evidence of a Resonant Structure in the $e^{+}{e}^{-}\to {\pi }^{+}{D}^0{D}^{*-}$ Cross Section between 4.05 and 4.60 GeV

The cross section of the process $e^{+}{e}^{-}\to {\pi }^{+}{D}^0{D}^{*-}$ for center-of-mass energies from 4.05 to 4.60 GeV is measured precisely using data samples collected with the BESIII detector operating at the BEPCII storage ring. Two enhancements are clearly visible in the cross section around 4.23 and 4.40 GeV. Using several models to describe the dressed cross section yields stable parameters for the first enhancement, which has a mass of $4228.6\pm 4.1\pm 6.3\mathrm{MeV}/c^2$ and a width of $77.0\pm 6.8\pm 6.3\mathrm{MeV}$, where the first uncertainties are statistical and the second ones are systematic. Our resonant mass is consistent with previous observations of the $Y(4220)$ state and the theoretical prediction of a $D{\overline{D}}_1(2420)$ molecule. This result is the first observation of $Y(4220)$ associated with an open-charm final state. Fits with three resonance functions with additional $Y(4260)$, $Y(4320)$, $Y(4360)$, $\psi (4415)$, or a new resonance do not show significant contributions from either of these resonances. The second enhancement is not from a single known resonance. It could contain contributions from $\psi (4415)$ and other resonances, and a detailed amplitude analysis is required to better understand this enhancement.

Figure 1

Fit to the distribution of $R{M}_{\text{cor}}(D^0{\pi }^{+})$ for the data sample at $\sqrt{s}=4.5995\mathrm{GeV}$. The black dots with error bars are data, the solid line (blue) describes the total fit, the dashed line (red) describes the signal shape, and the dotted and dash-dotted lines (black) describe BKG1 and BKG2, respectively. The pink vertical lines mark the signal region.

Figure 2

Fit to the dressed cross section of $e^{+}{e}^{-}\to {\pi }^{+}{D}^0{D}^{*-}$, where the black dots with error bars are the measured cross sections and the blue line shows the fit result. The error bars are statistical only. The pink dashed triple-dot line describes the phase-space contribution, the green dashed double-dot line describes the $R_2$ contribution, and the light blue dashed line describes the $R_1$ contribution.