Observation of χc1\chi_{c1} decays into vector meson pairs ϕϕ\phi\phi, ωω\omega\omega, and ωϕ\omega\phi

Decays of $\chi_{c1}$ to vector meson pairs $\phi\phi$, $\omega\omega$ and $\omega\phi$ are observed for the first time using $(106\pm4)\times 10^6$ \psip events accumulated at the BESIII detector at the BEPCII $e^+e^-$ collider. The branching fractions are measured to be $(4.4\pm 0.3\pm 0.5)\times 10^{-4}$, $(6.0\pm 0.3\pm 0.7)\times 10^{-4}$, and $(2.2\pm 0.6\pm 0.2)\times 10^{-5}$, for $\chi_{c1}\to \phi\phi$, $\omega\omega$, and $\omega\phi$, respectively. The observation of $\chi_{c1}$ decays into a pair of vector mesons $\phi\phi$, $\omega\omega$ and $\omega\phi$ indicates that the hadron helicity selection rule is significantly violated in $\chi_{cJ}$ decays. In addition, the measurement of $\chi_{cJ}\to \omega\phi$ gives the rate of doubly OZI-suppressed decay. Branching fractions for $\chi_{c0}$ and $\chi_{c2}$ decays into other vector meson pairs are also measured with improved precision.Comment: 4 pages, 2 figure

Does tea consumption during early pregnancy have an adverse effect on birth outcomes?

Background Tea, a common beverage, has been suggested to exhibit a number of health benefits. However, one of its active ingredients, caffeine, has been associated with preterm birth and low birthweight. We investigated whether tea consumption during early pregnancy is associated with an increased risk of preterm birth and abnormal foetal growth. Methods A total of 8775 pregnant women were included from the Born in Guangzhou Cohort Study. Tea consumption (type, frequency and strength) during their first trimester and social and demographic factors were obtained via questionnaires administered during pregnancy. Information on birth outcomes and complications during pregnancy was obtained from hospital medical records. Results Overall habitual tea drinking (≥1 serving/week) prevalence among pregnant women was low, at 16%. After adjustment for potential confounding factors (e.g. maternal age, educational level, monthly income) tea drinking during early pregnancy was not associated with an increased risk of preterm birth, small or large for gestational age (p>0.05). Conclusions We did not identify a consistent association between frequency of tea consumption or tea strength and adverse birth outcomes among Chinese pregnant women with low tea consumption. Our findings suggest that occasional tea drinking during pregnancy is not associated with increased risk of preterm birth or abnormal foetal growth. Given the high overall number of annual births in China, our findings have important public healt

Precision measurements of branching fractions for ψ′→π0Jψ \psi'\to\pi^0 J\psi and ηJψ\eta J\psi

We present a precision study of the \psip\to\pi^0 J/\psi and $\eta J/\psi$ decay modes. The measurements are obtained using $106\times10^6$ $\psi'$ events accumulated with the BESIII detector at the BEPCII \ee collider operating at a center-of-mass energy corresponding to the \psip mass. We obtain \mathcal{B}(\psip\to\pi^0 J/\psi)=(1.26\pm0.02{\rm (stat.)}\pm0.03{\rm (syst.)})\times 10^{-3} and \mathcal{B}(\psip\to\eta J/\psi)=(33.75\pm0.17{\rm (stat.)}\pm0.86{\rm (syst.)})\times 10^{-3}. The branching fraction ratio R=\frac{\mathcal{B}(\psip\to\pi^0 J/\psi)}{\mathcal{B}(\psip\to\eta J/\psi)} is determined to be $(3.74\pm0.06 {\rm(stat.)}\pm0.04 {\rm(syst.)})\times 10^{-2}$. The precision of these measurements of \mathcal{B}(\psip\to\pi^{0} J/\psi) and $R$ represent a significant improvement over previously published values.Comment: four figures, 12 page

Observation of Electromagnetic Dalitz decays J/\psi \to P e^+e^-

Based on a sample of (225.3\pm2.8)\times 10^{6} J/\psi events collected with the BESIII detector, the electromagnetic Dalitz decays of J/\psi \to P e^+e^-(P=\eta'/\eta/\pi^0) are studied. By reconstructing the pseudoscalar mesons in various decay modes, the decays J/\psi \to \eta' e^+e^-, J/\psi \to \eta e^+e^- and J/\psi \to \pi^0 e^+e^- are observed for the first time. The branching fractions are determined to be \mathcal{B}(J/\psi\to \eta' e^+e^-) = (5.81\pm0.16\pm0.31)\times10^{-5}, \mathcal{B}(J/\psi\to \eta e^+e^-) = (1.16\pm0.07\pm0.06)\times10^{-5}, and \mathcal{B}(J/\psi\to \pi^0 e^+e^-)=(7.56\pm1.32\pm0.50)\times10^{-7}, where the first errors are statistical and the second ones systematic

A theoretical study on impulse approximation of (e, 2e) reactions

The triple differential cross sections for electron impact ionization hydrogen (e, 2e) reactions are calculated as an example by use of the impulse approximation and Born approximation model at different coplanar asymmetric geometries. The results of the present work are compared with experimental data. The structures of the cross sections and the physical nature of these structures are discussed in detail. Moreover, the exchange effect contribution to the cross section is also discussed, which supports our earlier conclusions.</jats:p

ION BERNSTEIN WAVE COUPLING FOR POLOIDAL ELECTROSTATIC ANTENNA IN TOKAMAK

The coupling of Ion Bernstein Wave (IBW) excited at low-field side bv poloidal electrostatic antenna to plasma using uniform plasma model has been theoretically stydied. In order to more tally with the actual situation, the finiteness of antenna poloidal length and the nonzero poloidal wave number are considered. The computation of the coupling cord shows that the poloidal electrostatic antenna is able fo excited mostly IBW in plasma. The comparison between the poloidal electrostatic antenna and the conventional toroidal antenna for instrinsic spectral impedance, input impedance and wave energy fluxes is also made, from which it is concluded that the character of coupling IBW for both antenna is quite similar.</jats:p

A theoretical study on non-first-order effects of double differential cross sections

The double differential cross sections for electron impact ionization of hydrogen at different incident energies are calculated by use of the Brauner-Briggs-Klar (BBK) model and first order born approximation model. The results are compared with experimental data and other theoretical results. The non-first-order effects of the BBK model are analyzed and discussed in detail.</jats:p