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Register a new userMeasurement of $e^{+}e^{-} to pi^{0}pi^{0}psi(3686)$ at $sqrt{s}$ from 4.009 to 4.600 GeV and observation of a neutral charmoniumlike structure
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Using $e^{+}e^{-}$ collision data collected with the BESIII detector at the BEPCII collider corresponding to an integrated luminosity of 5.2 $fb^{-1}$ at center-of-mass energies ($sqrt{s}$) from 4.009 to 4.600 GeV, the process $e^{+}e^{-} to pi^{0} pi^{0}psi(3686)$ is studied for the first time. The corresponding Born cross sections are measured and found to be half of those of the reaction $e^{+}e^{-} to pi^{+}pi^{-}psi(3686)$. This is consistent with the expectation from isospin symmetry. Furthermore, the Dalitz plots for $pi^{0}pi^{0}psi(3686)$ are accordant with those of $pi^{+}pi^{-}psi(3686)$ at all energy points, and a neutral analogue to the structure in $pi^pm psi(3686)$ around 4040 MeV/$c^{2}$ first observed at $sqrt{s}$=4.416 GeV is observed in the isospin neutral mode at the same energy.
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We study the process e+e- to pi+pi-J/psi at a center-of-mass energy of 4.260 GeV using a 525 pb^{-1} data sample collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross section is measured to be (62.9pm 1.9pm 3.7) pb, consistent with the production of the Y(4260). We observe a structure at around 3.9 GeV/c^2 in the pi^pm J/psi mass spectrum, which we refer to as the Z_c(3900). If interpreted as a new particle, it is unusual in that it carries an electric charge and couples to charmonium. A fit to the pi^pm J/psi invariant mass spectrum, neglecting interference, results in a mass of (3899.0pm 3.6pm 4.9) MeV/c^2 and a width of (46pm 10pm 20) MeV. Its production ratio is measured to be R=frac{sigma(e+e- to pi^pm Z_c(3900)^mp to pi+pi-J/psi))} {sigma(e+e- to pi+pi-J/psi)}=(21.5pm 3.3pm 7.5)%. In all measurements the first errors are statistical and the second are systematic.
We study the process $e^{+}e^{-} rightarrow pi^{+}pi^{-}psi(3686)$ using 5.1 $fb^{-1}$ of data collected at 16 center-of-mass energy ($sqrt{s}$) points from 4.008 to 4.600$sim$GeV by the BESIII detector operating at the BEPCII collider. The measured Born cross sections for $e^{+}e^{-}rightarrow pi^{+}pi^{-}psi(3686)$ are consistent with previous results, but with much improved precision. A fit to the cross section shows contributions from two structures: the first has $M=4209.5pm7.4pm1.4$$sim$MeV/$c^{2}$ and $Gamma=80.1pm24.6pm2.9$$sim$MeV, and the second has $M=4383.8pm4.2pm0.8$$sim$MeV/c$^{2}$ and $Gamma=84.2pm12.5pm2.1$$sim$MeV, where the first errors are statistical and the second systematic. The lower-mass resonance is observed in the process $e^{+}e^{-}rightarrow pi^{+}pi^{-}psi(3686)$ for the first time with a statistical significance of $5.8sigma$. A charged charmonium-like structure is observed in the $pi^{pm}psi(3686)$ invariant mass spectrum for data at $sqrt{s} = 4.416~$GeV. A fit with an $S$-wave Breit-Wigner function yields a mass $M=4032.1pm2.4$~$MeV$^{2}$, where the errors are statistical only. However, there are still unresolved discrepancies between the fit model and data. The width of the intermediate state varies in a wide range for different kinematic regions within the data set. Therefore no simple interpretation of the data has been found, and a future data sample with larger statistics and more theoretical input will be required to better understand this issue.
Using data collected with the BESIII detector operating at the Beijing Electron Positron Collider at center-of-mass energies of $sqrt{s}=4.23$, 4.26, and 4.36~GeV, we observe $EEto pphc$ for the first time. The Born cross sections are measured and found to be about half of those of $EEto pi^+pi^-h_c$ within less than 2$sigma$. In the $pi^0h_c$ mass spectrum, a structure at 4.02~GeV/$c^2$ is found. It is most likely to be the neutral isospin partner of the $zcp^{pm}$ observed in the process of $EEto pi^+pi^-h_c$ is found. A fit to the $pi^0 h_c$ invariant mass spectrum, with the width of the $zcpn$ fixed to that of its charged isospin partner and possible interferences with non-$zcpn$ amplitudes neglected, gives a mass of ($4023.9pm 2.2 pm 3.8$)~MeV/$c^2$ for the $zcpn$, where the first error is statistical and the second systematic.
Using data samples with a total integrated luminosity of $20.1~rm fb^{-1}$ collected by the BESIII detector operating at the BEPCII collider, the cross section of the process $e^+e^- rightarrow pi^+pi^-psi(3686)$ is measured at center-of-mass energies between 4.0076 and 4.6984 GeV. The measured cross section is consistent with previous results, but with much improved precision. A fit to the measured energy-dependent cross section, which includes three Breit-Wigner functions and a non-resonant 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.
We report a study of the process $e^{+} e^{-} to (D^{*} bar{D}^{*})^{0} pi^0$ using $e^+e^-$ collision data samples with integrated luminosities of $1092 rm{pb}^{-1}$ at $sqrt{s}=4.23 rm{GeV}$ and $826 rm{pb}^{-1}$ at $sqrt{s}=4.26 rm{GeV}$ collected with the BESIII detector at the BEPCII storage ring. We observe a new neutral structure near the $(D^{*} bar{D}^{*})^{0}$ mass threshold in the $pi^0$ recoil mass spectrum, which we denote as $Z_{c}(4025)^{0}$. Assuming a Breit-Wigner line shape, its pole mass and pole width are determined to be $(4025.5^{+2.0}_{-4.7}pm3.1) rm{MeV}/c^2$ and $(23.0pm 6.0pm 1.0) rm{MeV}$, respectively. The Born cross sections of $e^{+}e^{-}to Z_{c}(4025)^{0} pi^0to (D^{*} bar{D}^{*})^{0}pi^0$ are measured to be $(61.6pm8.2pm9.0) rm{pb}$ at $sqrt{s}=4.23 rm{GeV}$ and $(43.4pm8.0pm5.4) rm{pb}$ at $sqrt{s}=4.26 rm{GeV}$. The first uncertainties are statistical and the second are systematic.
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