75 research outputs found

    Measurement of the proton form factor by studying e+eppˉe^{+} e^{-}\rightarrow p\bar{p}

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    Using data samples collected with the BESIII detector at the BEPCII collider, we measure the Born cross section of e+eppˉe^{+}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 (GE=GM)(|G_{E}|= |G_{M}|). In addition, the ratio of electric to magnetic form factors, GE/GM|G_{E}/G_{M}|, and GM|G_{M}| are extracted by fitting the polar angle distribution of the proton for the data samples with larger statistics, namely at s=\sqrt{s}= 2232.4 and 2400.0 MeV and a combined sample at s\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 GE/GM|G_{E}/G_{M}| ratios are close to unity and consistent with BaBar results in the same q2q^{2} region, which indicates the data are consistent with the assumption that GE=GM|G_{E}|=|G_{M}| within uncertainties.Comment: 13 pages, 24 figure

    Observation of the isospin-violating decay J/ψϕπ0f0(980)J/\psi \to \phi\pi^{0}f_{0}(980)

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    Using a sample of 1.31 billion J/ψJ/\psi events collected with the BESIII detector at the BEPCII collider, the decays J/ψϕπ+ππ0J/\psi \to \phi \pi^{+}\pi^{-}\pi^{0} and J/ψϕπ0π0π0J/\psi \to \phi \pi^{0}\pi^{0}\pi^{0} are investigated. The isospin violating decay J/ψϕπ0f0(980)J/\psi \to \phi \pi^{0} f_{0}(980) with f0(980)ππf_{0}(980) \to \pi\pi, is observed for the first time. The width of the f0(980)f_{0}(980) obtained from the dipion mass spectrum is found to be much smaller than the world average value. In the π0f0(980)\pi^{0} f_{0}(980) mass spectrum, there is evidence of f1(1285)f_1(1285) production. By studying the decay J/ψϕηJ/\psi \to \phi\eta', the branching fractions of ηπ+ππ0\eta' \to \pi^{+}\pi^{-}\pi^{0} and ηπ0π0π0\eta' \to \pi^{0}\pi^{0}\pi^{0}, as well as their ratio, are also measured.Comment: 10 pages, 10 figures, published in Phys. Rev.

    Measurement of the e+eηJ/ψe^{+}e^{-} \to \eta J/\psi cross section and search for e+eπ0J/ψe^{+}e^{-} \to \pi^{0} J/\psi at center-of-mass energies between 3.810 and 4.600~GeV

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    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+eηJ/ψe^{+}e^{-} \to \eta J/\psi and π0J/ψ\pi^0 J/\psi. Statistically significant signals of e+eηJ/ψe^{+}e^{-} \to \eta J/\psi are observed at s\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+eπ0J/ψe^{+}e^{-} \to \pi^{0} J/\psi are observed. The measured energy-dependent Born cross section for e+eηJ/ψe^{+}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

    An amplitude analysis of the π0π0\pi^{0}\pi^{0} system produced in radiative J/ψJ/\psi decays

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    An amplitude analysis of the π0π0\pi^{0}\pi^{0} system produced in radiative J/ψJ/\psi decays is presented. In particular, a piecewise function that describes the dynamics of the π0π0\pi^{0}\pi^{0} system is determined as a function of Mπ0π0M_{\pi^{0}\pi^{0}} from an analysis of the (1.311±0.011)×109(1.311\pm0.011)\times10^{9} J/ψJ/\psi decays collected by the BESIII detector. The goal of this analysis is to provide a description of the scalar and tensor components of the π0π0\pi^0\pi^0 system while making minimal assumptions about the properties or number of poles in the amplitude. Such a model-independent description allows one to integrate these results with other related results from complementary reactions in the development of phenomenological models, which can then be used to directly fit experimental data to obtain parameters of interest. The branching fraction of J/ψγπ0π0J/\psi \to \gamma \pi^{0}\pi^{0} is determined to be (1.15±0.05)×103(1.15\pm0.05)\times10^{-3}, where the uncertainty is systematic only and the statistical uncertainty is negligible.Comment: Submitted to Phys. Rev. D 19 pages, 4 figure

    Confirmation of a charged charmoniumlike state Zc(3885)Z_c(3885)^{\mp} in e+eπ±(DDˉ)e^+e^-\to\pi^{\pm}(D\bar{D}^*)^\mp with double DD tag

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    We present a study of the process e+eπ±(DDˉ)e^+e^-\to\pi^{\pm}(D\bar{D}^*)^{\mp} using data samples of 1092~pb1^{-1} at s=4.23\sqrt{s}=4.23~GeV and 826~pb1^{-1} at s=4.26\sqrt{s}=4.26~GeV collected with the BESIII detector at the BEPCII storage ring. With full reconstruction of the DD meson pair and the bachelor π±\pi^{\pm} in the final state, we confirm the existence of the charged structure Zc(3885)Z_c(3885)^{\mp} in the (DDˉ)(D\bar{D}^*)^{\mp} system in the two isospin processes e+eπ+D0De^+e^-\to\pi^+D^0D^{*-} and e+eπ+DD0e^+e^-\to\pi^+D^-D^{*0}. By performing a simultaneous fit, the statistical significance of Zc(3885)Zc(3885)^{\mp} signal is determined to be greater than 10σ\sigma, and its pole mass and width are measured to be MpoleM_{\rm{pole}}=(3881.7±\pm1.6(stat.)±\pm1.6(syst.))~MeV/c2c^2 and Γpole\Gamma_{\rm{pole}}=(26.6±\pm2.0(stat.)±\pm2.1(syst.))~MeV, respectively. The Born cross section times the (DDˉ)(D\bar{D}^*)^{\mp} branching fraction (σ(e+eπ±Zc(3885))×Br(Zc(3885)(DDˉ))\sigma(e^+e^-\to\pi^{\pm}Z_{c}(3885)^{\mp}) \times Br(Z_{c}(3885)^{\mp}\to(D\bar{D}^*)^{\mp})) is measured to be (141.6±7.9(stat.)±12.3(syst.)) pb(141.6\pm7.9(\text{stat.})\pm12.3(\text{syst.}))~\text{pb} at s=4.23\sqrt{s}=4.23~GeV and (108.4±6.9(stat.)±8.8(syst.)) pb(108.4\pm6.9(\text{stat.})\pm8.8(\text{syst.}))~\text{pb} at s=4.26\sqrt{s}=4.26~GeV. The polar angular distribution of the π±\pi^{\pm}-Zc(3885)Z_c(3885)^{\mp} system is consistent with the expectation of a quantum number assignment of JP=1+J^P=1^+ for Zc(3885)Z_c(3885)^{\mp}

    Search for the Y(4140)Y(4140) via e+eγϕJ/ψe^{+} e^{-} \to \gamma \phi J/\psi at s=\sqrt{s}= 4.23, 4.26 and 4.36 GeV

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    Using data samples collected at center-of-mass energies s=4.23\sqrt{s} = 4.23, 4.26, and 4.36 GeV with the BESIII detector operating at the BEPCII storage ring, we search for the production of the charmoniumlike state Y(4140)Y(4140) through a radiative transition followed by its decay to ϕJ/ψ\phi J/\psi. No significant signal is observed and upper limits on σ[e+eγY(4140)]B(Y(4140)ϕJ/ψ)\sigma[e^{+} e^{-} \rightarrow \gamma Y(4140)] \cdot \mathcal{B}(Y(4140)\rightarrow \phi J/\psi) at the 90%90\% confidence level are estimated as 0.35, 0.28, and 0.33 pb at s=4.23\sqrt{s} = 4.23, 4.26, and 4.36 GeV, respectively

    The histology of ovarian cancer: worldwide distribution and implications for international survival comparisons (CONCORD-2)

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    Objective Ovarian cancers comprise several histologically distinct tumour groups with widely different prognosis. We aimed to describe the worldwide distribution of ovarian cancer histology and to understand what role this may play in international variation in survival. Methods The CONCORD programme is the largest population-based study of global trends in cancer survival. Data on 681,759 women diagnosed during 1995â\u80\u932009 with cancer of the ovary, fallopian tube, peritoneum and retroperitonum in 51 countries were included. We categorised ovarian tumours into six histological groups, and explored the worldwide distribution of histology. Results During 2005â\u80\u932009, type II epithelial tumours were the most common. The proportion was much higher in Oceania (73.1%), North America (73.0%) and Europe (72.6%) than in Central and South America (65.7%) and Asia (56.1%). By contrast, type I epithelial tumours were more common in Asia (32.5%), compared with only 19.4% in North America. From 1995 to 2009, the proportion of type II epithelial tumours increased from 68.6% to 71.1%, while the proportion of type I epithelial tumours fell from 23.8% to 21.2%. The proportions of germ cell tumours, sex cord-stromal tumours, other specific non-epithelial tumours and tumours of non-specific morphology all remained stable over time. Conclusions The distribution of ovarian cancer histology varies widely worldwide. Type I epithelial, germ cell and sex cord-stromal tumours are generally associated with higher survival than type II tumours, so the proportion of these tumours may influence survival estimates for all ovarian cancers combined. The distribution of histological groups should be considered when comparing survival between countries and regions

    Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks, 1990-2015: A systematic analysis for the Global Burden of Disease Study 2015

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    Background: The Global Burden of Diseases, Injuries, and Risk Factors Study 2015 provides an up-to-date synthesis of the evidence for risk factor exposure and the attributable burden of disease. By providing national and subnational assessments spanning the past 25 years, this study can inform debates on the importance of addressing risks in context. Methods: We used the comparative risk assessment framework developed for previous iterations of the Global Burden of Disease Study to estimate attributable deaths, disability-adjusted life-years (DALYs), and trends in exposure by age group, sex, year, and geography for 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks from 1990 to 2015. This study included 388 risk-outcome pairs that met World Cancer Research Fund-defined criteria for convincing or probable evidence. We extracted relative risk and exposure estimates from randomised controlled trials, cohorts, pooled cohorts, household surveys, census data, satellite data, and other sources. We used statistical models to pool data, adjust for bias, and incorporate covariates. We developed a metric that allows comparisons of exposure across risk factors—the summary exposure value. Using the counterfactual scenario of theoretical minimum risk level, we estimated the portion of deaths and DALYs that could be attributed to a given risk. We decomposed trends in attributable burden into contributions from population growth, population age structure, risk exposure, and risk-deleted cause-specific DALY rates. We characterised risk exposure in relation to a Socio-demographic Index (SDI). Findings: Between 1990 and 2015, global exposure to unsafe sanitation, household air pollution, childhood underweight, childhood stunting, and smoking each decreased by more than 25%. Global exposure for several occupational risks, high body-mass index (BMI), and drug use increased by more than 25% over the same period. All risks jointly evaluated in 2015 accounted for 57·8% (95% CI 56·6–58·8) of global deaths and 41·2% (39·8–42·8) of DALYs. In 2015, the ten largest contributors to global DALYs among Level 3 risks were high systolic blood pressure (211·8 million [192·7 million to 231·1 million] global DALYs), smoking (148·6 million [134·2 million to 163·1 million]), high fasting plasma glucose (143·1 million [125·1 million to 163·5 million]), high BMI (120·1 million [83·8 million to 158·4 million]), childhood undernutrition (113·3 million [103·9 million to 123·4 million]), ambient particulate matter (103·1 million [90·8 million to 115·1 million]), high total cholesterol (88·7 million [74·6 million to 105·7 million]), household air pollution (85·6 million [66·7 million to 106·1 million]), alcohol use (85·0 million [77·2 million to 93·0 million]), and diets high in sodium (83·0 million [49·3 million to 127·5 million]). From 1990 to 2015, attributable DALYs declined for micronutrient deficiencies, childhood undernutrition, unsafe sanitation and water, and household air pollution; reductions in risk-deleted DALY rates rather than reductions in exposure drove these declines. Rising exposure contributed to notable increases in attributable DALYs from high BMI, high fasting plasma glucose, occupational carcinogens, and drug use. Environmental risks and childhood undernutrition declined steadily with SDI; low physical activity, high BMI, and high fasting plasma glucose increased with SDI. In 119 countries, metabolic risks, such as high BMI and fasting plasma glucose, contributed the most attributable DALYs in 2015. Regionally, smoking still ranked among the leading five risk factors for attributable DALYs in 109 countries; childhood underweight and unsafe sex remained primary drivers of early death and disability in much of sub-Saharan Africa. Interpretation: Declines in some key environmental risks have contributed to declines in critical infectious diseases. Some risks appear to be invariant to SDI. Increasing risks, including high BMI, high fasting plasma glucose, drug use, and some occupational exposures, contribute to rising burden from some conditions, but also provide opportunities for intervention. Some highly preventable risks, such as smoking, remain major causes of attributable DALYs, even as exposure is declining. Public policy makers need to pay attention to the risks that are increasingly major contributors to global burden. Funding: Bill & Melinda Gates Foundation

    Measurement of transverse energy at midrapidity in Pb-Pb collisions at root s(NN)=2.76 TeV

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    We report the transverse energy (ET) measured with ALICE at midrapidity in Pb-Pb collisions at root s(NN) = 2.76 TeV as a function of centrality. The transverse energy was measured using identified single-particle tracks. The measurement was cross checked using the electromagnetic calorimeters and the transverse momentum distributions of identified particles previously reported by ALICE. The results are compared to theoretical models as well as to results from other experiments. The mean ET per unit pseudorapidity (eta), , in 0%-5% central collisions is 1737 +/- 6(stat.) +/- 97(sys.) GeV. We find a similar centrality dependence of the shape of as a function of the number of participating nucleons to that seen at lower energies. The growth in at the LHC energies exceeds extrapolations of low-energy data. We observe a nearly linear scaling of with the number of quark participants. With the canonical assumption of a 1 fm/c formation time, we estimate that the energy density in 0%-5% central Pb-Pb collisions at root s(NN) = 2.76 TeV is 12.3 +/- 1.0 GeV/fm(3) and that the energy density at the most central 80 fm(2) of the collision is at least 21.5 +/- 1.7 GeV/fm(3). This is roughly 2.3 times that observed in 0%-5% central Au-Au collisions at root s(NN) = 200 GeV.Peer reviewe
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