We present measurements of the charmonium state $h_c(^1P_1)$ made with 106M $\psi'$ events collec... more We present measurements of the charmonium state $h_c(^1P_1)$ made with 106M $\psi'$ events collected by BESIII at BEPCII. Clear signals are observed for $\psi'\to\pi^0 h_c$ with and without the subsequent radiative decay $h_c\to\gamma\eta_c$. First measurements of the absolute branching ratios $\mathcal{B}(\psi' \to\pi^0 h_c) = (8.4 \pm 1.3 \pm 1.0) \times 10^{-4}$ and $\mathcal{B}(h_c \to \gamma \eta_c) = (54.3 \pm 6.7 \pm5.2)%$ are presented. A statistics-limited determination of the previously unmeasured $h_c$ width leads to an upper limit $\Gamma(h_c)<1.44 $MeV (90% confidence). Measurements of $M(h_c) = 3525.40 \pm 0.13 \pm 0.18 $MeV/$c^2$ and $\mathcal{B}(\psi'\to \pi^0 h_c) \times \mathcal{B}(h_c \to \gamma\eta_c) = (4.58 \pm 0.40 \pm 0.50) \times 10^{-4}$ are consistent with previous results.
Using a sample of $(225.2\pm 2.8)\times 10^6$ $J/\psi$ events collected with the Beijing Spectrom... more Using a sample of $(225.2\pm 2.8)\times 10^6$ $J/\psi$ events collected with the Beijing Spectrometer (BESIII) at the Beijing Electron-Positron Collider, CP and $P$ violating decays of $\eta$, $\eta'$ and $\etac$ into $\pi^+\pi^-$ and $\pi^0 \pi^0$ are searched for in $\jpsi$ radiative decays. No significant $\eta$, $\eta'$ or $\etac$ signal is observed, and 90% confidence level upper limits of $\BR(\eta \to \pi^+\pi^-)<3.9\times 10^{-4}$, $\BR(\eta' \to \pi^+\pi^-)<5.5\times 10^{-5}$, $\BR(\etac \to \pi^+\pi^-)<1.3\times 10^{-4}$, $\BR(\eta \to \pi^0 \pi^0)<6.9\times 10^{-4}$, $\BR(\eta' \to \pi^0 \pi^0)<4.5\times 10^{-4}$ and $\BR(\etac \to \pi^0 \pi^0)<4.2\times 10^{-5}$ are obtained.
With a sample of (225.2±2.8)×106 J/ψ events registered in the BESIII detector, J/ψ→γπ+π-η' is stu... more With a sample of (225.2±2.8)×106 J/ψ events registered in the BESIII detector, J/ψ→γπ+π-η' is studied using two η' decay modes: η'→π+π-η and η'→γρ0. The X(1835), which was previously observed by BESII, is confirmed with a statistical significance that is larger than 20σ. In addition, in the π+π-η' invariant-mass spectrum, the X(2120) and the X(2370), are observed with statistical significances larger than 7.2σ and 6.4σ, respectively. For the X(1835), the angular distribution of the radiative photon is consistent with expectations for a pseudoscalar.
We present measurements of the charmonium state $h_c(^1P_1)$ made with 106M $\psi'$ events collec... more We present measurements of the charmonium state $h_c(^1P_1)$ made with 106M $\psi'$ events collected by BESIII at BEPCII. Clear signals are observed for $\psi'\to\pi^0 h_c$ with and without the subsequent radiative decay $h_c\to\gamma\eta_c$. First measurements of the absolute branching ratios $\mathcal{B}(\psi' \to\pi^0 h_c) = (8.4 \pm 1.3 \pm 1.0) \times 10^{-4}$ and $\mathcal{B}(h_c \to \gamma \eta_c) = (54.3 \pm 6.7 \pm5.2)%$ are presented. A statistics-limited determination of the previously unmeasured $h_c$ width leads to an upper limit $\Gamma(h_c)<1.44 $MeV (90% confidence). Measurements of $M(h_c) = 3525.40 \pm 0.13 \pm 0.18 $MeV/$c^2$ and $\mathcal{B}(\psi'\to \pi^0 h_c) \times \mathcal{B}(h_c \to \gamma\eta_c) = (4.58 \pm 0.40 \pm 0.50) \times 10^{-4}$ are consistent with previous results.
Using a sample of $(225.2\pm 2.8)\times 10^6$ $J/\psi$ events collected with the Beijing Spectrom... more Using a sample of $(225.2\pm 2.8)\times 10^6$ $J/\psi$ events collected with the Beijing Spectrometer (BESIII) at the Beijing Electron-Positron Collider, CP and $P$ violating decays of $\eta$, $\eta'$ and $\etac$ into $\pi^+\pi^-$ and $\pi^0 \pi^0$ are searched for in $\jpsi$ radiative decays. No significant $\eta$, $\eta'$ or $\etac$ signal is observed, and 90% confidence level upper limits of $\BR(\eta \to \pi^+\pi^-)<3.9\times 10^{-4}$, $\BR(\eta' \to \pi^+\pi^-)<5.5\times 10^{-5}$, $\BR(\etac \to \pi^+\pi^-)<1.3\times 10^{-4}$, $\BR(\eta \to \pi^0 \pi^0)<6.9\times 10^{-4}$, $\BR(\eta' \to \pi^0 \pi^0)<4.5\times 10^{-4}$ and $\BR(\etac \to \pi^0 \pi^0)<4.2\times 10^{-5}$ are obtained.
With a sample of (225.2±2.8)×106 J/ψ events registered in the BESIII detector, J/ψ→γπ+π-η' is stu... more With a sample of (225.2±2.8)×106 J/ψ events registered in the BESIII detector, J/ψ→γπ+π-η' is studied using two η' decay modes: η'→π+π-η and η'→γρ0. The X(1835), which was previously observed by BESII, is confirmed with a statistical significance that is larger than 20σ. In addition, in the π+π-η' invariant-mass spectrum, the X(2120) and the X(2370), are observed with statistical significances larger than 7.2σ and 6.4σ, respectively. For the X(1835), the angular distribution of the radiative photon is consistent with expectations for a pseudoscalar.
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