| Abstract: | Using about 23 $mathrm{fb^{-1}}$ of data collected with the BESIII detector
operating at the BEPCII storage ring, a precise measurement of the $e^{+}e^{-}
ightarrow pi^{+}pi^{-}J/psi$ Born cross section is performed at
center-of-mass energies from 3.7730 to 4.7008 GeV. Two structures, identified
as the $Y(4220)$ and the $Y(4320)$ states, are observed in the energy-dependent
cross section with a significance larger than $10sigma$. The masses and widths
of the two structures are determined to be ($M, Gamma$) =
($4221.4pm1.5pm2.0$ MeV/$c^{2}$, $41.8pm2.9pm2.7$ MeV) and ($M, Gamma$) =
($4298pm12pm26$ MeV/$c^{2}$, $127pm17pm10$ MeV), respectively. A small
enhancement around 4.5 GeV with a significance about $3sigma$, compatible with
the $psi(4415)$, might also indicate the presence of an additional resonance
in the spectrum. The inclusion of this additional contribution in the fit to
the cross section affects the resonance parameters of the $Y(4320)$ state. |
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