Geometric global quantum discord

Geometric quantum discord, proposed by Dakic, Vedral, and Brukner [Phys. Rev. Lett. 105 (2010) 190502], is an important measure for bipartite correlations. In this paper, we generalize it to multipartite states, we call the generalized version geometric global quantum discord (GGQD). We characterize GGQD in different ways, and provide some special states which allow analytical GGQD.Comment: 8 pages,no figure;added a lower bound for GGQD to version

Observation of ηc→ωω\eta_c\to\omega\omega in J/ψ→γωωJ/\psi\to\gamma\omega\omega

Using a sample of $(1310.6\pm7.0)\times10^6$ $J/\psi$ events recorded with the BESIII detector at the symmetric electron positron collider BEPCII, we report the observation of the decay of the $(1^1 S_0)$ charmonium state $\eta_c$ into a pair of $\omega$ mesons in the process $J/\psi\to\gamma\omega\omega$. The branching fraction is measured for the first time to be $\mathcal{B}(\eta_c\to\omega\omega)= (2.88\pm0.10\pm0.46\pm0.68)\times10^{-3}$, where the first uncertainty is statistical, the second systematic and the third is from the uncertainty of $\mathcal{B}(J/\psi\to\gamma\eta_c)$. The mass and width of the $\eta_c$ are determined as $M=(2985.9\pm0.7\pm2.1)\,$MeV/$c^2$ and $\Gamma=(33.8\pm1.6\pm4.1)\,$MeV.Comment: 13 pages, 6 figure

Observation and study of the decay J/ψ→ϕηη′J/\psi\rightarrow\phi\eta\eta'

We report the observation and study of the decay $J/\psi\rightarrow\phi\eta\eta'$ using $1.3\times{10^9}$ $J/\psi$ events collected with the BESIII detector. Its branching fraction, including all possible intermediate states, is measured to be $(2.32\pm0.06\pm0.16)\times{10^{-4}}$. We also report evidence for a structure, denoted as $X$, in the $\phi\eta'$ mass spectrum in the $2.0-2.1$ GeV/$c^2$ region. Using two decay modes of the $\eta'$ meson ($\gamma\pi^+\pi^-$ and $\eta\pi^+\pi^-$), a simultaneous fit to the $\phi\eta'$ mass spectra is performed. Assuming the quantum numbers of the $X$ to be $J^P = 1^-$, its significance is found to be 4.4$\sigma$, with a mass and width of $(2002.1 \pm 27.5 \pm 21.4)$ MeV/$c^2$ and $(129 \pm 17 \pm 9)$ MeV, respectively, and a product branching fraction $\mathcal{B}(J/\psi\rightarrow\eta{}X)\times{}\mathcal{B}(X\rightarrow\phi\eta')=(9.8 \pm 1.2 \pm 1.7)\times10^{-5}$. Alternatively, assuming $J^P = 1^+$, the significance is 3.8$\sigma$, with a mass and width of $(2062.8 \pm 13.1 \pm 7.2)$ MeV/$c^2$ and $(177 \pm 36 \pm 35)$ MeV, respectively, and a product branching fraction $\mathcal{B}(J/\psi\rightarrow\eta{}X)\times{}\mathcal{B}(X\rightarrow\phi\eta')=(9.6 \pm 1.4 \pm 2.0)\times10^{-5}$. The angular distribution of $J/\psi\rightarrow\eta{}X$ is studied and the two $J^P$ assumptions of the $X$ cannot be clearly distinguished due to the limited statistics. In all measurements the first uncertainties are statistical and the second systematic.Comment: 10 pages, 6 figures and 4 table

Observation of Ds+→pnˉD^+_s\rightarrow p\bar{n} and confirmation of its large branching fraction

The baryonic decay $D^+_s\rightarrow p\bar{n}$ is observed, and the corresponding branching fraction is measured to be $(1.21\pm0.10\pm0.05)\times10^{-3}$, where the first uncertainty is statistical and second systematic. The data sample used in this analysis was collected with the BESIII detector operating at the BEPCII $e^+e^-$ double-ring collider with a center-of-mass energy of 4.178~GeV and an integrated luminosity of 3.19~fb$^{-1}$. The result confirms the previous measurement by the CLEO Collaboration and is of greatly improved precision, which may deepen our understanding of the dynamical enhancement of the W-annihilation topology in the charmed meson decays

Observation of an anomalous line shape of the η′π+π−\eta^{\prime}\pi^{+}\pi^{-} mass spectrum near the ppˉp\bar{p} mass threshold in J/ψ→γη′π+π−J/\psi\rightarrow\gamma\eta^{\prime}\pi^{+}\pi^{-}

Using $1.09\times10^{9}$ $J/\psi$ events collected by the BESIII experiment in 2012, we study the $J/\psi\rightarrow\gamma\eta^{\prime}\pi^{+}\pi^{-}$ process and observe a significant abrupt change in the slope of the $\eta^{\prime}\pi^{+}\pi^{-}$ invariant mass distribution at the proton-antiproton ($p\bar{p}$) mass threshold. We use two models to characterize the $\eta^{\prime}\pi^{+}\pi^{-}$ line shape around $1.85~\text{GeV}/c^{2}$: one which explicitly incorporates the opening of a decay threshold in the mass spectrum (Flatt\'{e} formula), and another which is the coherent sum of two resonant amplitudes. Both fits show almost equally good agreement with data, and suggest the existence of either a broad state around $1.85~\text{GeV}/c^{2}$ with strong couplings to $p\bar{p}$ final states or a narrow state just below the $p\bar{p}$ mass threshold. Although we cannot distinguish between the fits, either one supports the existence of a $p\bar{p}$ molecule-like state or bound state with greater than $7\sigma$ significance

Search for the radiative transitions ψ(3770)→γηc\psi(3770)\to\gamma\eta_c and γηc(2S)\gamma\eta_c(2S)

By using a 2.92 fb$^{-1}$ data sample taken at $\sqrt{s} = 3.773$ GeV with the BESIII detector operating at the BEPCII collider, we search for the radiative transitions $\psi(3770)\to\gamma\eta_c$ and $\gamma\eta_c(2S)$ through the hadronic decays $\eta_c(\eta_c(2S))\to K^0_SK^\pm\pi^\mp$. No significant excess of signal events above background is observed. We set upper limits at a 90% confidence level for the product branching fractions to be $\mathcal{B}(\psi(3770)\to\gamma\eta_c)\times \mathcal{B}(\eta_c\to K^0_SK^\pm\pi^\mp) < 1.6\times10^{-5}$ and $\mathcal{B}(\psi(3770)\to\gamma\eta_c(2S))\times \mathcal{B}(\eta_c(2S)\to K^0_SK^\pm\pi^\mp) < 5.6\times10^{-6}$. Combining our result with world-average values of $\mathcal{B}(\eta_c(\eta_c(2S))\to K^0_SK^\pm\pi^\mp)$, we find the branching fractions $\mathcal{B}(\psi(3770)\to\gamma\eta_c) < 6.8\times10^{-4}$ and $\mathcal{B}(\psi(3770)\to\gamma\eta_c(2S)) < 2.0\times10^{-3}$ at a 90% confidence level.Comment: 10 pages, 4 figure

Observation of J/ψ→ppˉa0(980)J/\psi \rightarrow p\bar{p}a_{0}(980) at BESIII

Using $2.25\times10^{8}$ $J/\psi$ events collected with the BESIII detector at the BEPCII storage rings, we observe for the first time the process $J/\psi\rightarrow p\bar{p}a_{0}(980)$, $a_{0}(980)\rightarrow \pi^{0}\eta$ with a significance of $6.5\sigma$ ($3.2\sigma$ including systematic uncertainties). The product branching fraction of $J/\psi\rightarrow p\bar{p}a_{0}(980)\rightarrow p\bar{p}\pi^{0}\eta$ is measured to be $(6.8\pm1.2\pm1.3)\times 10^{-5}$, where the first error is statistical and the second is systematic. This measurement provides information on the $a_{0}$ production near threshold coupling to $p\bar{p}$ and improves the understanding of the dynamics of $J/\psi$ decays to four body processes.Comment: 8 pages, 7 figure

Measurement of proton electromagnetic form factors in e+e−→ppˉe^+e^- \to p\bar{p} in the energy region 2.00-3.08 GeV

The process of $e^+e^- \rightarrow p\bar{p}$ is studied at 22 center-of-mass energy points ($\sqrt{s}$) from 2.00 to 3.08 GeV, exploiting 688.5~pb$^{-1}$ of data collected with the BESIII detector operating at the BEPCII collider. The Born cross section~($\sigma_{p\bar{p}}$) of $e^+e^- \rightarrow p\bar{p}$ is measured with the energy-scan technique and it is found to be consistent with previously published data, but with much improved accuracy. In addition, the electromagnetic form-factor ratio ($|G_{E}/G_{M}|$) and the value of the effective ($|G_{\rm{eff}}|$), electric ($|G_E|$) and magnetic ($|G_M|$) form factors are measured by studying the helicity angle of the proton at 16 center-of-mass energy points. $|G_{E}/G_{M}|$ and $|G_M|$ are determined with high accuracy, providing uncertainties comparable to data in the space-like region, and $|G_E|$ is measured for the first time. We reach unprecedented accuracy, and precision results in the time-like region provide information to improve our understanding of the proton inner structure and to test theoretical models which depend on non-perturbative Quantum Chromodynamics

Observation of hch_{c} radiative decay hc→γη′h_{c} \rightarrow \gamma \eta' and evidence for hc→γηh_{c} \rightarrow \gamma \eta

A search for radiative decays of the $P$-wave spin singlet charmonium resonance $h_c$ is performed based on $4.48 \times 10^{8}$ $\psi'$ events collected with the BESIII detector operating at the BEPCII storage ring. Events of the reaction channels $h_{c} \rightarrow \gamma \eta'$ and $\gamma \eta$ are observed with a statistical significance of $8.4 \sigma$ and $4.0 \sigma$, respectively, for the first time. The branching fractions of $h_{c} \rightarrow \gamma \eta'$ and $h_{c} \rightarrow \gamma \eta$ are measured to be $\mathcal{B}(h_{c} \rightarrow \gamma \eta')=(1.52 \pm 0.27 \pm 0.29)\times10^{-3}$ and $\mathcal{B}(h_{c} \rightarrow \gamma \eta)=(4.7 \pm 1.5 \pm 1.4)\times10^{-4}$, respectively, where the first errors are statistical and the second are systematic uncertainties.Comment: 7 pages, 2 figure