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BESIII Collaboration: M. Ablikim
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The decays $J/psito pbar{p}$ and $J/psito nbar{n}$ have been investigated with a sample of 225.2 million $J/psi$ events collected with the BESIII detector at the BEPCII $e^+e^-$ collider. The branching fractions are determined to be $mathcal{B}(J/psito pbar{p})=(2.112pm0.004pm0.031)times10^{-3}$ and $mathcal{B}(J/psito nbar{n})=(2.07pm0.01pm0.17)times10^{-3}$. Distributions of the angle $theta$ between the proton or anti-neutron and the beam direction are well described by the form $1+alphacos^2theta$, and we find $alpha=0.595pm0.012pm0.015$ for $J/psito pbar{p}$ and $alpha=0.50pm0.04pm0.21$ for $J/psito nbar{n}$. Our branching-fraction results suggest a large phase angle between the strong and electromagnetic amplitudes describing the $J/psito Nbar{N}$ decay.
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Using a data sample of $1.31 times 10^{9}$ $J/psi$ events accumulated with the BESIII detector, the decay $J/psito pbar{p}phi$ is studied via two decay modes, $phito K^{0}_{S}K^{0}_{L}$ and $phito K^{+}K^{-}$. The branching fraction of $J/psito pbar{p}phi$ is measured to be $mathcal{B}(J/psito pbar{p}phi)=[5.23pm0.06(mbox{stat})pm0.33(mbox{syst})]times10^{-5}$, which agrees well with a previously published measurement, but with a significantly improved precision. No evident enhancement near the $pbar{p}$ mass threshold, denoted as $X(pbar{p})$, is observed, and the upper limit on the branching fraction of $J/psito X(pbar{p})phito pbar{p}phi$ is determined to be $mathcal{B}(J/psito X(pbar{p})phito pbar{p}phi)<2.1times10^{-7}$ at the 90% confidence level.
We present the first study of the process $J/psi rightarrow gammaetapi^{0}$ using $(223.7pm1.4)times10^{6}$ $J/psi$ events accumulated with the BESIII detector at the BEPCII facility. The branching fraction for $J/psi rightarrow gammaetapi^{0}$ is measured to be $mathcal{B}(J/psi rightarrow gammaetapi^{0}) =(2.14pm0.18(stat)pm0.25(syst))times10^{-5}$. With a Bayesian approach, the upper limits of the branching fractions $mathcal{B}(J/psi rightarrow gamma a_{0}(980),a_0(980)rightarrowetapi^0)$ and $mathcal{B}(J/psi rightarrow gamma a_{2}(1320),a_2(1320)rightarrowetapi^0)$ are determined to be $2.5times10^{-6}$ and $6.6times10^{-6}$ at the 95% confidence level, respectively. All of these measurements are given for the first time.
Data are presented on the reaction J/psi--> p pbar eta using 7.8 million J/psi triggers collected by the BEjing Spectrometer (BES). A partial wave analysis is performed. A clear enhancement near the p eta(pbar eta) threshold is observed. It is fitted with a JP=1/2- resonance with mass $M= 1530pm 10$ MeV and width $Gamma = 95pm 25$ MeV. In addition, there is a peak around 1650 MeV with JP=1/2- preferred also, fitted with $M =1647pm 20$ MeV and $Gamma = 145^{+80}_{-45}$ MeV. These two N* resonances are believed to be the two well established states, S11(1535) and S11(1650), respectively. It is the first partial wave study of the production of these resonances from J/psi decays.
A partial-wave analysis of the decay $J/psi to K^+K^-pi^0$ has been made using $(223.7pm1.4)times 10^{6}$ $J/psi$ events collected with the BESIII detector in 2009. The analysis, which is performed within the isobar-model approach, reveals contributions from $K^*_2(1430)^pm$, $K^*_2(1980)^pm$ and $K^*_4(2045)^pm$ decaying to $K^pmpi^0$. The two latter states are observed in $J/psi$ decays for the first time. Two resonance signals decaying to $K^+K^-$ are also observed. These contributions can not be reliably identified and their possible interpretations are discussed. The measured branching fraction $B(J/psi to K^+K^-pi^0)$ of $(2.88pm0.01pm0.12)times10^{-3}$ is more precise than previous results. Branching fractions for the reported contributions are presented as well. The results of the partial-wave analysis differ significantly from those previously obtained by BESII and BABAR.
A search for the charged lepton flavor violating decay $J/psito e^{pm}tau^{mp}$ with $tau^{mp} to pi^{mp}pi^0 u_{tau}$ is performed with about $10$ billion $J/ psi$ events collected with the BESIII detector at the BEPCII. No significant signal is observed, and an upper limit is set on the branching fraction $mathcal{B}(J/psito e^{pm}tau^{mp})<7.5times10^{-8}$ at the 90$%$ confidence level. This improves the previously published limit by two orders of magnitude.
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