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تسجيل مستخدم جديدStudy of $psi(3686)topi^0 h_c, h_ctogammaeta_c$ via $eta_c$ exclusive decays
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The process $psi(3686) to pi^0 h_c, h_c to gamma eta_c$ has been studied with a data sample of $106 pm 4$ million $psi(3686)$ events collected with the BESIII detector at the BEPCII storage ring. The mass and width of the $P$-wave charmonium spin-singlet state $h_c(^1P_1)$ are determined by simultaneously fitting distributions of the $pi^0$ recoil mass for 16 exclusive $eta_c$ decay modes. The results, $M(hc) = 3525.31 pm 0.11 {rm (stat.)} pm 0.14 {rm (syst.)}$,MeV/$c^2$ and $Gamma(hc) = 0.70 pm 0.28 pm 0.22$,MeV, are consistent with and more precise than previous measurements. We also determine the branching ratios for the 16 exclusive $eta_c$ decay modes, five of which have not been measured previously. New measurements of the $eta_c$ line-shape parameters in the $E1$ transition $h_ctogammaeta_c$ are made by selecting candidates in the $h_c$ signal sample and simultaneously fitting the hadronic mass spectra for the 16 $eta_c$ decay channels. The resulting $eta_c$ mass and width values are $M(eta_c) = 2984.49 pm 1.16 pm 0.52$,MeV/$c^2$ and $Gamma(eta_c) = 36.4 pm 3.2 pm 1.7$,MeV.
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We study the decays of $J/psi$ and $psi(3686)$ to the final states $Sigma(1385)^{0}barSigma(1385)^{0}$ and $Xi^0barXi^{0}$ based on a single baryon tag method using data samples of $(1310.6 pm 7.0) times 10^{6}$ $J/psi$ and $(447.9 pm 2.9) times 10^{
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ovariant tensor amplitude approach. The dominant contribution is found to be $J/psi$ and $psi(3686)$ decays to $rhoeta^prime$. In the $J/psi$ decay, the branching fraction ${cal B}(J/psito rhoeta^prime)$ is determined to be $(7.90pm0.19(mathrm{stat})pm0.49(mathrm{sys}))times 10^{-5}$. Two solutions are found in the $psi(3686)$ decay, and the corresponding branching fraction ${cal B}(psi(3686)to rhoeta^prime)$ is $(1.02pm0.11(mathrm{stat})pm0.24(mathrm{sys}))times 10^{-5}$ for the case of constructive interference, and $(5.69pm1.28(mathrm{stat})pm2.36(mathrm{sys}))times 10^{-6}$ for destructive interference. As a consequence, the ratios of branching fractions between $psi(3686)$ and $J/psi$ decays to $rhoeta^prime$ are calculated to be $(12.9pm1.4(mathrm{stat})pm3.1(mathrm{sys}))$% and $(7.2pm1.6(mathrm{stat})pm3.0(mathrm{sys}))$%, respectively. We also determine the inclusive branching fractions of $J/psi$ and $psi(3686)$ decays to $pi^+pi^-eta^prime$ to be $(1.36pm0.02(mathrm{stat})pm0.08(mathrm{sys}))times 10^{-4}$ and $(1.51pm0.14(mathrm{stat})pm 0.23(mathrm{sys}))times 10^{-5}$, respectively.
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^{-} +c.c.$. No significant signals are observed and the corresponding upper limits on the branching fractions at the $90%$ confidence level are determined to be $Br(J/psi to D^{0} e^{+}e^{-} +c.c.)< 8.5times 10^{-8}$ and $Br (psi(3686) to D^{0} e^{+}e^{-} +c.c.)<1.4times 10^{-7}$, respectively. Our limit on $Br(J/psi to D^{0} e^{+}e^{-} +c.c.)$ is more stringent by two orders of magnitude than the previous results, and the $Br(psi(3686) to D^{0} e^{+}e^{-} +c.c.)$ is measured for the first time.
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