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Register a new userSearches for isospin-violating transitions $chi_{c0,2} rightarrow pi^{0} eta_{c}$
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We present the first upper-limit measurement of the branching fractions of the isospin-violating transitions $chi_{c0,2} rightarrow pi^{0} eta_{c}$. The measurements are performed using $106times 10^{6}$ $psi(3686)$ events accumulated with the BESIII detector at the BEPCII $e^{+}e^{-}$ collider at a center-of-mass energy corresponding to the $psi(3686)$ mass. We obtained upper limits on the branching fractions at a 90% confidence level of $B(chi_{c0} rightarrow pi^{0} eta_{c}) < 1.6 times 10^{-3}$ and $B(chi_{c2} rightarrow pi^{0} eta_{c}) < 3.2 times 10^{-3}$.
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Using data samples collected at center of mass energies of $sqrt{s}$ = 4.009, 4.226, 4.257, 4.358, 4.416 and 4.599 GeV with the BESIII detector operating at the BEPCII storage ring, we search for the isospin violating decay $Y(4260)rightarrow J/psi eta pi^{0}$. No signal is observed, and upper limits on the cross section $sigma(e^{+}e^{-}rightarrow J/psi eta pi^{0})$ at the 90% confidence level are determined to be 3.6, 1.7, 2.4, 1.4, 0.9 and 1.9 pb, respectively.
A study of $B^{0}_{s} to eta_{c} phi$ and $B^{0}_{s} to eta_{c} pi^{+}pi^{-}$ decays is performed using $pp$ collision data corresponding to an integrated luminosity of 3.0$,rm fb^{-1}$, collected with the LHCb detector in Run~1 of the LHC. The observation of the decay $B^{0}_{s} to eta_{c} phi$ is reported, where the $eta_{c}$ meson is reconstructed in the $pbar p$, $K^+K^-pi^+pi^-$, $pi^+pi^-pi^+pi^-$ and $K^+K^-K^+K^-$ decay modes and the $phi(1020)$ in the $K^+ K^-$ decay mode. The decay $B^{0}_{s} to J/psi phi$ is used as a normalisation channel. Evidence is also reported for the decay $B^{0}_{s} to eta_{c} pi^{+}pi^{-}$, where the $eta_{c}$ meson is reconstructed in the $pbar p$ decay mode, using the decay $B^{0}_{s} to J/psi pi^+ pi^-$ as a normalisation channel. The measured branching fractions are begin{eqnarray*} {mathcal B (B^{0}_{s} to eta_{c} phi)} &=& left(5.01 pm 0.53 pm 0.27 pm 0.63 right) times 10^{-4} ,, onumber {mathcal B (B^{0}_{s} to eta_{c} pi^+ pi^-)} &=& left(1.76 pm 0.59 pm 0.12 pm 0.29 right) times 10^{-4} ,, end{eqnarray*} where in each case the first uncertainty is statistical, the second systematic and the third uncertainty is due to the limited knowledge of the external branching fractions.
We study $eta_{rm c}$ production at center-of-mass energies $sqrt{s}$ from 4.18 to 4.60 GeV in $e^+e^-$ annihilation data collected with the BESIII detector operating at the BEPCII storage ring, corresponding to 7.3 fb$^{-1}$ of integrated luminosity. We measure the cross sections of the three different exclusive reactions $e^+e^-rightarrow eta_{rm c}pi^+ pi^-pi^0$, $e^+e^- rightarrow eta_{rm c}pi^+ pi^-$, and $e^+e^- rightarrow eta_{rm c}pi^0gamma$. We find significant $eta_{rm c}$ production in $e^+e^-rightarrow eta_{rm c}pi^+ pi^-pi^0$ at $sqrt{s}$ of 4.23 GeV and 4.26 GeV and observe a significant energy-dependent Born cross section that we measure to be consistent with the production via the intermediate $Y(4260)$ resonance. In addition, we perform a search for a charmonium-like $Z_{rm c}$ state close to the $Dbar{D}$ threshold that decays to $eta_{rm c}pi$, involving ground state charmonium, and observe no signal. Corresponding upper limits on the cross section of $eta_{rm c}$ and $Z_{rm c}$ production are provided, where the yields are not found to be significant.
Using a sample of $447.9times 10^6$ $psi(3686)$ events collected with the BESIII detector in 2009 and 2012, we study the decays $chi_{c0,2}to$ $etaeta$ and $etaeta$. The decays $chi_{c2}toetaeta$, $chi_{c0}toetaeta$ and $chi_{c2}toetaeta$ are observed for the first time with statistical significances of $9.6sigma$, $13.4sigma$ and $7.5sigma$, respectively. The branching fractions are determined to be $mathcal{B}(chi_{c0}toetaeta) =(2.19pm0.03pm0.14)times10^{-3}$, $mathcal{B}(chi_{c2}toetaeta) = (4.76pm0.56pm0.38)times10^{-5}$, $mathcal{B}(chi_{c0}toetaeta) = (8.92pm0.84pm0.65)times10^{-5}$ and $mathcal{B}(chi_{c2}toetaeta) = (2.27pm0.43pm0.25)times10^{-5}$, where the first uncertainties are statistical and the second systematic. The precision for the measurement of $mathcal{B}(chi_{c0}toetaeta)$ is significantly improved compared to previous measurements. Based on the measured branching fractions, the role played by the doubly and singly Okubo-Zweig-Iizuka disconnected transition amplitudes for $chi_{c0,2}$ decays into pseudoscalar meson pairs can be clarified.
We search for the M1 radiative transition psi(3686) to gammaeta_{c}(2S) by reconstructing the exclusive eta_{c}(2S) to K_{S}^{0}K^{pm}pi^{mp}pi^{+}pi^{-} decay using 1.06 times 10^8 psi(3686) events collected with the BESIII detector. The signal is observed with a statistical significance of greater than 4 standard deviations. The measured mass of the eta_{c}(2S) is 3646.9 pm 1.6(stat) pm 3.6(syst) MeV/c^2, and the width is 9.9 pm 4.8(stat) pm 2.9(syst) MeV/c^2. The product branching fraction is measured to be B(psi(3686) to gammaeta_{c}(2S)) times B(eta_{c}(2S) to K_{S}^{0}K^{pm}pi^{mp}pi^{+}pi^{-}) = (7.03 pm 2.10(stat) pm 0.70(syst)) times 10^{-6}. This measurement complements a previous BESIII measurement of psi(3686) to gammaeta_{c}(2S) with eta_{c}(2S) to K_{S}^{0} K^{pm}pi^{mp} and K^{+}K^{-}pi^{0}.
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