Measurements of $psi(3686) to K^{-} Lambda bar{Xi}^{+} +c.c.$ and $psi(3686) to gamma K^{-} Lambda bar{Xi}^{+} +c.c$

Using a sample of $1.06times10^8 psip$ events produced in $e^+e^-$ collisions at $sqrt{s}$ = 3.686 GeV and collected with the BESIII detector at the BEPCII collider, we present studies of the decays $klx+c.c.$ and $gklx+c.c.$. We observe two hyperons, $Xi(1690)^-$ and $Xi(1820)^-$, in the $K^-Lambda$ invariant mass distribution in the decay $klx+c.c.$ with significances of $4.9 sigma$ and $6.2 sigma$, respectively. The branching fractions of $klx+c.c.$, $ksx+c.c.$, $psiptogamma chi_{cJ}to gamma K^- Lambda bar{Xi}^+ +c.c.$ $(J=0, 1, 2)$, and $psipto Xi(1690/1820)^{-} bar{Xi}^++c.c$ with subsequent decay $Xi(1690/1820)^-to K^-Lambda$ are measured for the first time.

Evidence for $e^+e^-togammachi_{c1, 2}$ at center-of-mass energies from 4.009 to 4.360 GeV

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.

Study of $e^+e^-toomegachi_{cJ}$ at center-of-mass energies from 4.21 to 4.42 GeV

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 $9sigma$.

Search for the $eta_c(2S)/h_cto pbar{p}$ decays and measurements of the $chi_{cJ}to pbar{p}$ branching fractions

Using a sample of $1.06times10^{8}~psi(3686)$ events collected with the BESIII detector at BEPCII, the decays $eta_{c}(2S)to pbar{p}$ and $h_{c}to pbar{p}$ are searched for, where $eta_c(2S)$ and $h_c$ are reconstructed in the decay chains $psi(3686)togammaeta_{c}(2S)$, $eta_{c}(2S)to pbar{p}$ and $psi(3686)topi^{0}h_{c}$, $h_{c}to pbar{p}$, respectively. No significant signals are observed. The upper limits of the product branching fractions are determined to be $mathcal{B}(psi(3686)togammaeta_c(2S))timesmathcal{B}(eta_{c}(2S)to pbar{p})<1.4times10^{-6}$ and $mathcal{B}(psi(3686)topi^0h_c)timesmathcal{B}(h_{c}to pbar{p})<1.3times10^{-7}$ at the 90% C.L.. The branching fractions for $chi_{cJ}to pbar{p}$ $(J=0,~1,~2)$ are also measured to be $(24.5pm0.8pm1.3,~8.6pm0.5pm0.5,~8.4pm0.5pm0.5)times10^{-5}$, which are the worlds most precise measurements.

Observation of $e^{+} e^{-} to gamma X(3872)$ at BESIII

With data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies from 4.009 to 4.420 GeV, the process $e^{+} e^{-} to gamma X(3872)$ is observed for the first time with a statistical significance of $6.3sigma$. The measured mass of the $X(3872)$ is ($3871.9pm 0.7_{rm stat.}pm 0.2_{rm sys.}$) MeV/$c^2$, in agreement with previous measurements. Measurements of the product of the cross section $sigma[e^{+} e^{-} to gamma X(3872)]$ and the branching fraction $mathcal{B}[X(3872) to pi^{+} pi^{-} J/psi]$ at center-of-mass energies 4.009, 4.229, 4.260, and 4.360 GeV are reported. Our measurements are consistent with expectations for the radiative transition process $Y(4260) to gamma X(3872)$.

Study of the near-threshold $omegaphi$ mass enhancement in doubly OZI suppressed $J/psi to gammaomegaphi$ decays

A 2.25$times10^8$ $jpsi$ event sample accumulated with the BESIII detector is used to study the doubly OZI suppressed decay modes $jpsitogammaof$, $omegatoppp$, $phitokk$. A strong deviation ($>$ 30$sigma$) from three-body $jpsitogammaomegaphi$ phase space is observed near the $omegaphi$ mass threshold that is consistent with a previous observation reported by the BESII experiment. A partial wave analysis with a tensor covariant amplitude that assumes that the enhancement is due to the presence of a resonance, the X(1810), is performed, and confirms that the spin-parity of the X(1810) is $0^{++}$. The mass and width of the X(1810) are determined to be $M=1795pm7$(stat)$^{+13}_{-5}$(syst)$pm$19(mod) MeV/$c^2$ and $Gamma=95pm10$(stat)$^{+21}_{-34}$(syst)$pm$75(mod) MeV/$c^2$, respectively, and the product branching fraction is measured to be ${cal B}(jpsitogamma X(1810))times{cal B}(X(1810)toof)=(2.00pm0.08$(stat)$^{+0.45}_{-1.00}$(syst)$pm$1.30(mod))$times10^{-4}$. %where the first error is the statistical error and the second the systematical error. These results are consistent within errors with those of the BESII experiment.