Evidence of a resonant structure in the $e^+e^-\to \pi^+D^0D^{*-}$ cross section between 4.05 and 4.60 GeV

TL;DR

This paper reports the first observation of the Y(4220) resonance in the $e^+e^- o \pi^+D^0D^{*-}$ process, providing precise measurements and suggesting it may be a $Dar{D}_1(2420)$ molecule, with additional structures observed.

Contribution

The study provides the first evidence of the Y(4220) resonance in an open-charm final state and measures its parameters with high precision, confirming its consistency with previous observations.

Findings

Resonant structure at 4.23 GeV consistent with Y(4220)

First observation of Y(4220) in open-charm final state

Additional enhancement around 4.40 GeV not from known resonances

Abstract

The cross section of the process $e^+e^-\to \pi^+D^0D^{*-}$ 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 $4228.6 \pm 4.1 \pm 6.3 \un{MeV}/c^2$ and a width of $77.0 \pm 6.8 \pm 6.3 \un{MeV}$, 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 $D\bar{D}_1(2420)$ 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.