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Register a new userObservation of $J/psito gammaetapi^{0}$
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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.
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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.
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.
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.
Using a sample of 1.31 billion $J/psi$ events collected with the BESIII detector at the BEPCII collider, the decays $J/psi to phi pi^{+}pi^{-}pi^{0}$ and $J/psi to phi pi^{0}pi^{0}pi^{0}$ are investigated. The isospin violating decay $J/psi to phi pi^{0} f_{0}(980)$ with $f_{0}(980) to pipi$, is observed for the first time. The width of the $f_{0}(980)$ obtained from the dipion mass spectrum is found to be much smaller than the world average value. In the $pi^{0} f_{0}(980)$ mass spectrum, there is evidence of $f_1(1285)$ production. By studying the decay $J/psi to phieta$, the branching fractions of $eta to pi^{+}pi^{-}pi^{0}$ and $eta to pi^{0}pi^{0}pi^{0}$, as well as their ratio, are also measured.
The $B_s^0 rightarrow J/psi phi phi$ decay is observed in $pp$ collision data corresponding to an integrated luminosity of 3 fb$^{-1}$ recorded by the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV. This is the first observation of this decay channel, with a statistical significance of 15 standard deviations. The mass of the $B_s^0$ meson is measured to be $5367.08,pm ,0.38,pm, 0.15$ MeV/c$^2$. The branching fraction ratio $mathcal{B}(B_s^0 rightarrow J/psi phi phi)/mathcal{B}(B_s^0 rightarrow J/psi phi)$ is measured to be $0.0115,pm, 0.0012, ^{+0.0005}_{-0.0009}$. In both cases, the first uncertainty is statistical and the second is systematic. No evidence for non-resonant $B_s^0 rightarrow J/psi phi K^+ K^-$ or $B_s^0 rightarrow J/psi K^+ K^- K^+ K^-$ decays is found.
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