Using data samples collected with the BESIII detector at the BEPCII collider, we measure the Born cross section of \(e^{+}e^{-}\rightarrow p\bar{p}\) at 12 center-of-mass energies from 2232.4 to ...3671.0 MeV. The corresponding effective electromagnetic form factor of the proton is deduced under the assumption that the electric and magnetic form factors are equal \((|G_{E}|= |G_{M}|)\). In addition, the ratio of electric to magnetic form factors, \(|G_{E}/G_{M}|\), and \(|G_{M}|\) are extracted by fitting the polar angle distribution of the proton for the data samples with larger statistics, namely at \(\sqrt{s}=\) 2232.4 and 2400.0 MeV and a combined sample at \(\sqrt{s}\) = 3050.0, 3060.0 and 3080.0 MeV, respectively. The measured cross sections are in agreement with recent results from BaBar, improving the overall uncertainty by about 30\%. The \(|G_{E}/G_{M}|\) ratios are close to unity and consistent with BaBar results in the same \(q^{2}\) region, which indicates the data are consistent with the assumption that \(|G_{E}|=|G_{M}|\) within uncertainties.
We report a measurement of the branching fraction of \(\psi(3770)\to\gamma\chi_{c1}\) and search for the transition \(\psi(3770)\rightarrow \gamma \chi_{c2}\) based on 2.92~fb\(^{-1}\) of \(e^+e^-\) ...data accumulated at \(\sqrt{s}=3.773\)~GeV with the BESIII detector at the BEPCII collider. The measured branching fraction of \(\psi(3770) \rightarrow \gamma \chi_{c1}\) is \(\mathcal B(\psi(3770) \rightarrow \gamma \chi_{c1})=(2.48 \pm 0.15 \pm 0.23) \times 10^{-3}\), which is the most precise measurement to date. The upper limit on the branching fraction of \(\psi(3770)\rightarrow \gamma \chi_{c2}\) at a \(90\%\) confidence level is \(\mathcal B(\psi(3770) \rightarrow \gamma \chi_{c2})<0.64 \times 10^{-3}\). The corresponding partial widths are \(\Gamma(\psi(3770) \to \gamma \chi_{c1}) =(67.5\pm 4.1\pm 6.7)\)~keV and \(\Gamma(\psi(3770) \to \gamma \chi_{c2}) < 17.4\)~keV.
We report the observation of the \(X(3823)\) in the process \(e^+e^-\to \pi^+\pi^-X(3823) \to \pi^+\pi^-\gamma\chi_{c1}\) with a statistical significance of \(6.2\sigma\), in data samples at ...center-of-mass energies \(\sqrt{s}=\)4.230, 4.260, 4.360, 4.420 and 4.600~GeV collected with the BESIII detector at the BEPCII electron positron collider. The measured mass of the \(X(3823)\) is \((3821.7\pm 1.3\pm 0.7)\)~MeV/\(c^2\), where the first error is statistical and the second systematic, and the width is less than \(16\)~MeV at the 90\% confidence level. The products of the Born cross sections for \(e^+e^-\to \pi^+\pi^-X(3823)\) and the branching ratio \(\mathcal{B}X(3823)\to \gamma\chi_{c1,c2}\) are also measured. These measurements are in good agreement with the assignment of the \(X(3823)\) as the \(\psi(1^3D_2)\) charmonium state.
Using a data sample of 106 million \(\psi(3686)\) events collected with the BESIII detector operated at the BEPCII storage ring, we study for the first time the decay \(\chi_{cJ}\to\phi K^{0}_S ...K^{\pm}\pi^{\mp}\) and \(\chi_{cJ}\to\phi K^{+} K^{-}\pi^{0}\) in the E1 radiative transition \(\psi(3686)\to\gamma\chi_{cJ}\). The decays are dominated by the three-body decay \(\chi_{cJ}\to \phi K^*(892)\bar{K}\). We measure branching fractions for this reaction via the neutral and charged \(K^*(892)\) and find them consistent with each other within the expectation of isospin symmetry. In the \(K\bar{K}\pi\) invariant mass distribution a structure near the \(K^*(892)\bar{K}\) mass threshold is observed, and the corresponding mass and width are measured to be \(1412\pm4(\mathrm{stat.})\pm8(\mathrm{sys.}) \mathrm{MeV}/c^2\) and \(\Gamma\) = \(84\pm12(\mathrm{stat.})\pm40(\mathrm{sys.}) \mathrm{MeV}\), respectively. The observed state favors an assignment to the \(h_1(1380)\), considering its possible \(J^{PC}\) and comparing its mass, width and decay mode to those reported in the Particle Data Group.
Using 2.92 fb\(^{-1}\) of electron-positron annihilation data collected at a center-of-mass energy of \(\sqrt{s}= 3.773\) GeV with the BESIII detector, we present an improved measurement of the ...branching fraction \(\mathcal{B}(D^+ \to \omega e^+ \nu_{e}) = (1.63\pm0.11\pm0.08)\times 10^{-3}\). The parameters defining the corresponding hadronic form factor ratios at zero momentum transfer are determined for the first time, we measure them to be \(r_V = 1.24\pm0.09\pm0.06\) and \(r_2 = 1.06\pm0.15 \pm 0.05\). The first and second uncertainties are statistical and systematic, respectively. We also search for the decay \(D^+ \to \phi e^+ \nu_{e}\). An improved upper limit \(\mathcal{B}(D^+ \to \phi e^+ \nu_{e}) < 1.3 \times 10^{-5}\) is set at 90\% confidence level.
We report the first observation of the Dalitz decay \(\eta' \to \gamma e^+e^-\), based on a data sample of 1.31 billion \(J/\psi\) events collected with the BESIII detector. The \(\eta'\) mesons are ...produced via the \(J/\psi \to \gamma \eta'\) decay process. The ratio \(\Gamma(\eta' \to \gamma e^+ e^-)/\Gamma(\eta'\to\gamma\gamma)\) is measured to be \((2.13\pm0.09(\text{stat.})\pm0.07(\text{sys.}))\times10^{-2}\). This corresponds to a branching fraction \({\cal B}(\eta' \to \gamma e^+e^-)= (4.69 \pm0.20(\text{stat.})\pm0.23(\text{sys.}))\times10^{-4}\). The transition form factor is extracted and different expressions are compared to the measured dependence on the \(e^+e^-\) invariant mass. The results are consistent with the prediction of the Vector Meson Dominance model.
Using a sample of \(1.06\times10^8\ \psip\) events produced in \(e^+e^-\) collisions at \(\sqrt{s}\) = 3.686 GeV and collected with the BESIII detector at the BEPCII collider, we present studies of ...the decays \(\klx+c.c.\) and \(\gklx+c.c.\). We observe two hyperons, \(\Xi(1690)^-\) and \(\Xi(1820)^-\), in the \(K^-\Lambda\) invariant mass distribution in the decay \(\klx+c.c.\) with significances of \(4.9 \sigma\) and \(6.2 \sigma\), respectively. The branching fractions of \(\klx+c.c.\), \(\ksx+c.c.\), \(\psip\to\gamma \chi_{cJ}\to \gamma K^- \Lambda \bar{\Xi}^+ +c.c.\) \((J=0,\ 1,\ 2)\), and \(\psip\to \Xi(1690/1820)^{-} \bar{\Xi}^++c.c\) with subsequent decay \(\Xi(1690/1820)^-\to K^-\Lambda\) are measured for the first time.
Using data samples collected with the BESIII detector operating at the BEPCII collider at center-of-mass energies from 3.810 to 4.600 GeV, we perform a study of \(e^{+}e^{-} \to \eta J/\psi\) and ...\(\pi^0 J/\psi\). Statistically significant signals of \(e^{+}e^{-} \to \eta J/\psi\) are observed at \(\sqrt{s}\) = 4.190, 4.210, 4.220, 4.230, 4.245, 4.260, 4.360 and 4.420 GeV, while no signals of \(e^{+}e^{-} \to \pi^{0} J/\psi\) are observed. The measured energy-dependent Born cross section for \(e^{+}e^{-} \to \eta J/\psi\) shows an enhancement around 4.2~GeV. The measurement is compatible with an earlier measurement by Belle, but with a significantly improved precision.
This study compares diencephalic and temporal lobe amnesics on a memory task in which the encoding of temporal context is essential for accurate performance. On trial 1 subjects were shown four ...pictures and asked to discriminate them from distractors one minute later. On the three subsequent trials the same procedure was used except that items previously used as distractors became targets and vice versa. The results showed that both groups performed close to ceiling on trial 1. On trials 2, 3, and 4, however, the diencephalic group showed poorer accuracy than the temporal lobe group. These results indicate that the diencephalic amnesics have greater difficulty encoding distinctive contexts across trials 2, 3, and 4 than do the temporal lobe group. Explanations of this difference are discussed briefly.
PDF
