No Arabic abstract
During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5~fb$^{-1}$ of $e^+e^-$ collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV. These data samples are primarily used for the study of excited charmonium and charmoniumlike states. By analyzing the di-muon process $e^{+}e^{-} to (gamma_{rm ISR/FSR}) mu^{+}mu^{-}$, we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV. Through a run-by-run study, we find that the center-of-mass energies were stable throughout most of the data-taking period.
The process $e^{+}e^{-} rightarrow phieta$ is studied at 22 center-of-mass energy points ($sqrt{s}$) between 2.00 and 3.08 GeV using 715 pb$^{-1}$ of data collected with the BESIII detector. The measured Born cross section of $e^{+}e^{-} rightarrow phieta$ is found to be consistent with {textsl{BABAR}} measurements, but with improved precision. A resonant structure around 2.175 GeV is observed with a significance of 6.9$sigma$ with mass ($2163.5pm6.2pm3.0$) MeV/$c^{2}$ and width ($31.1_{-11.6}^{+21.1}pm1.1$) MeV, where the first uncertainties are statistical and the second are systematic.
Based on data samples collected with the BESIII detector at the BEPCII collider at 9 center-of-mass energies from 4.21 to 4.42 GeV, we search for the production of $e^+e^-to omegachi_{cJ}$ ($J$=0, 1, 2). The process $e^+e^-to omegachi_{c0}$ is observed for the first time, and the Born cross sections at $sqrt{s}$=4.23 and 4.26 GeV are measured to be $(55.4pm 6.0pm 5.9)$ and $(23.7pm 5.3pm 3.5)$ pb, respectively, where the first uncertainties are statistical and the second are systematic. The $omegachi_{c0}$ signals at the other 7 energies and $e^+e^-to omegachi_{c1}$ and $omegachi_{c2}$ signals are not significant, and the upper limits on the cross sections are determined. By examining the $omegachi_{c0}$ cross section as a function of center-of-mass energy, we find that it is inconsistent with the line shape of the $Y(4260)$ observed in $e^+ e^-topi^+pi^-J/psi$. Assuming the $omegachi_{c0}$ signals come from a single resonance, we extract mass and width of the resonance to be $(4230pm8pm6)$ MeV/$c^2$ and $(38pm12pm2)$ MeV, respectively, and the statistical significance is more than $9sigma$.
Using a total of $5.25~{rm fb}^{-1}$ of $e^{+}e^{-}$ collision data with center-of-mass energies from 4.236 to 4.600 GeV, we report the first observation of the process $e^{+}e^{-}to etapsi(2S)$ with a statistical significance of $5sigma$. The data sets were collected by the BESIII detector operating at the BEPCII storage ring. We measure the yield of events integrated over center-of-mass energies and also present the energy dependence of the measured cross section.
The state $Y(2175)$ is observed in the process $e^+ e^- to eta Y(2175)$ at center-of-mass energies between 3.7 and 4.6$sim$GeV with a statistical significance larger than $10sigma$ using data collected with the BESIII detector operating at the BEPCII storage ring. This is the first observation of the $Y(2175)$ in this process. The mass and width of the $Y(2175)$ are determined to be ($2135pm 8pm 9$)~MeV/$c^2$ and ($104pm 24pm 12$)~MeV, respectively, and the production cross section of $e^+ e^- to eta Y(2175)to etaphi f_{0}(980)to etaphi pi^+ pi^-$ is at a several hundred femtobarn level. No significant signal for the process $e^+ e^- to eta Y(2175)$ is observed and the upper limit on $sigma(e^+ e^- to eta Y(2175))/sigma(e^+ e^- to eta Y(2175))$ is estimated to be 0.43 at the 90% confidence level. We also search for $psi(3686) to eta Y(2175)$. No significant signal is observed, indicating a strong suppression relative to the corresponding $J/psi$ decay, in violation of the 12% rule.
Based on $e^+e^-$ annihilation data samples collected with the BESIII detector at the BEPCII collider at 13 center of mass energies from 4.008 to 4.600 GeV, measurements of the Born cross section of $e^{+}e^{-}rightarrow p bar{p} pi^{0}$ are performed. No significant resonant structure is observed in the measured energy-dependent cross section. The upper limit on the Born cross section of $e^{+}e^{-}rightarrow Y(4260) rightarrow p bar{p} pi^{0}$ at the 90% C.L. is determined to be 0.01 pb.