2,638 research outputs found

    Measurement of meson transition form factors at BESIII

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    Meson transition form factors describe the coupling of photons and hadrons. They are an important input to the calculations of the light-by-light scattering contribution of the anomalous magnetic moment of the muon. At the BESIII experiment in Beijing, the transition form factors of pseudoscalar mesons are studied in their Dalitz decays, in their radiative production in e+ee^+e^- annihilation, and in their production in two-photon scattering. All relevant kinematic regimes are covered. An overview of the recent results and the status of the ongoing analyses is provided.Comment: Talk presented CIPANP2018. 9 pages, LaTeX, 4 pdf figure

    Anisotropic flow of identified particles in Pb--Pb collisions at sNN=5.02\sqrt{s_{\rm NN}} = 5.02 TeV

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    Anisotropic flow is sensitive to the shear (η/s)(\eta/s) and bulk (ζ/s\zeta/s) viscosity of the quark-gluon plasma created in heavy-ion collisions, as well as the initial state of such collisions and hadronization mechanisms. In these proceedings, elliptic (v2v_2) and higher harmonic (v3,v4v_3, v_4) flow coefficients of π±\pi^{\pm}, K±K^{\pm}, p(p)(\overline{\rm{p}}) and the ϕ\phi-meson, are presented for Pb-Pb collisions at the highest-ever center-of-mass energy of sNN\sqrt{s_{\rm NN}} = 5.02 TeV. Comparisons to hydrodynamic calculations (IP-Glasma, MUSIC, UrQMD) are shown to constrain the initial conditions and viscosity of the medium

    Azimuthal anisotropy of charged jet production in sNN\mathbf{\sqrt{{\textit s}_{\rm NN}}} = 2.76 TeV Pb--Pb collisions

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    Measurements of charged jet production with respect to the second-order harmonic event plane, quantified as v2ch jetv_{2}^{\mathrm{ch~jet}}, in sNN\sqrt{s_{\mathrm{NN}}} = 2.76 TeV Pb--Pb collisions are presented. The contribution of hydrodynamic flow to the underlying event energy is corrected for on a jet-by-jet basis. Remaining effects from instrumental resolution and regional fluctuations in the energy density of the underlying event are corrected for by unfolding. Significant v2ch jetv_{2}^{\mathrm{ch~jet}} is observed in semi-central collisions. Qualitative agreement is found with v2ch+emjetv_{2}^{\mathrm{ch+em jet}} of jets reconstructed from charged and neutral fragments and v2v_2 of single charged particles, as well as with predictions from the JEWEL Monte Carlo model.Comment: 4 pages, 5 figures, to appear in the proceedings of Quark Matter 2015, KOBE, Japa

    Measurement of Hadronic Cross Sections at BESIII

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    The uncertainties of the Standard Model prediction of the anomalous magnetic moment of the muon are currently completely dominated by hadronic contributions. The largest contribution is due to the hadronic vacuum polarization. Hadronic cross sections measured at e+ee^+e^- colliders can be exploited as experimental input to improve the calculations, making use of the optical theorem. At the BESIII experiment in Beijing these cross sections are determined using different methods. At center-of-mass energies above 2 GeV exclusive and inclusive cross sections can be measured in an energy scan. Additionally, cross sections can be determined starting from the π+π\pi^+\pi^- mass threshold using the method of Initial State Radiation. An overview of the recent results and the status of the analyses is provided.Comment: Talk presented CIPANP2018. 10 pages, LaTeX, 7 pdf figure

    Thermophysical properties of warm dense hydrogen

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    We study the thermophysical properties of warm dense hydrogen using quantum molecular dynamics simulations. New results are presented for the pair distribution functions, the equation of state, the Hugoniot curve, and the reflectivity. We compare with available experimental data and predictions of the chemical picture. Especially, we discuss the nonmetal-to-metal transition which occurs at about 40 GPa in the dense fluid

    Interpolation formula for the electrical conductivity of nonideal plasmas

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    On the basis of a quantum-statistical approach to the electrical conductivity of nonideal plasmas we derive analytical results in the classical low-density regime, in the degenerate Born limit, and for the contribution of the Debye-Onsager relaxation effect. These explicit results are used to construct an improved interpolation formula of the electrical conductivity valid in a wide range of temperature and density which allows to compare with available experimental data of nonideal plasmas.Comment: 7 pages, 1 tabl

    Proceedings of the International PrimeNet Workshop

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    These are the proceedings of the PrimeNet Workshop, held in September 16-18, 2010, at the campus of Instituto Superior T\'ecnico in Lisbon, Portugal. This workshop is part of the activities in the project "Study of Strongly Interacting Matter" (acronym HadronPhysics2), which is an integrating activity of the Seventh Framework Program of EU. This HP2 project contains several activities, one of them being the network PrimeNet having the focus on Meson Physics in Low-Energy QCD. This network is created to exchange information on experimental and theoretical ongoing activities on mainly eta and eta-prime physics at different European accelerator facilities and institutes.Comment: 78 pages; Each talk is represented by an extended abstrac
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