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Register a new userEvidence for $e^+e^-togammachi_{c1, 2}$ at center-of-mass energies from 4.009 to 4.360 GeV
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Using data samples collected at center-of-mass energies of $sqrt{s}$ = 4.009, 4.230, 4.260, and 4.360 GeV with the BESIII detector operating at the BEPCII collider, we perform a search for the process $e^+e^-togammachi_{cJ}$ $(J = 0, 1, 2)$ and find evidence for $e^+e^-togammachi_{c1}$ and $e^+e^-togammachi_{c2}$ with statistical significances of 3.0$sigma$ and 3.4$sigma$, respectively. The Born cross sections $sigma^{B}(e^+e^-togammachi_{cJ})$, as well as their upper limits at the 90% confidence level are determined at each center-of-mass energy.
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We present first evidence for the process $e^+e^-to gammaeta_c(1S)$ at six center-of-mass energies between 4.01 and 4.60~GeV using data collected by the BESIII experiment operating at BEPCII. These data sets correspond to a total integrated luminosity of 4.6~fb$^{-1}$. We measure the Born cross section at each energy using a combination of twelve $eta_c(1S)$ decay channels. Because the significance of the signal is marginal at each energy ($le3.0sigma$), we also combine all six energies under various assumptions for the energy-dependence of the cross section. If the process is assumed to proceed via the $Y(4260)$, we measure a peak Born cross section $sigma_{mathrm{ peak}}(e^+e^-togammaeta_c(1S)) = 2.11 pm 0.49 (mathrm{stat.}) pm 0.36 (mathrm{syst.})$~pb with a statistical significance of 4.2$sigma$.
Using a 478 pb$^{-1}$ data sample collected with the BESIII detector operating at the BEPCII storage ring at a center-of-mass energy of $sqrt{s}=4.009$ GeV, the production of $e^{+}e^{-}to eta Jpsi$ is observed for the first time with a statistical significance of greater than $10sigma$. The Born cross section is measured to be $(32.1pm 2.8 pm 1.3)$ pb, where the first error is statistical and the second systematic. Assuming the $eta Jpsi$ signal is from a hadronic transition of the $psi(4040)$, the fractional transition rate is determined to be ${cal B}(psi(4040)to eta Jpsi)=(5.2pm 0.5pm 0.2pm 0.5)times 10^{-3}$, where the first, second, and third errors are statistical, systematic, and the uncertainty from the $psi(4040)$ resonant parameters, respectively. The production of $e^{+}e^{-} to pi^0 Jpsi$ is searched for, but no significant signal is observed, and ${cal B}(psi(4040)to pi^0 Jpsi) < 2.8 times 10^{-4}$ is obtained at the 90% confidence level.
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.
Using data taken at 23 center-of-mass energies between 4.0 and 4.6 GeV with the BESIII detector at the BEPCII collider and with a total integrated luminosity of approximately $15$ fb$^{-1}$, the process $e^+e^-to 2(p bar{p})$ is studied for the first time. The Born cross sections for $e^+e^-to 2(p bar{p})$ are measured, and no significant structure is observed in the lineshape. The baryon pair ($pp$ and $bar{p}bar{p}$) invariant mass spectra are consistent with phase space, therefore no hexaquark or di-baryon state is found.
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