325,864 research outputs found

    Chiral expansion of the π0γγ\pi^0\rightarrow\gamma\gamma decay width

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    A chiral field theory of mesons has been applied to study the contribution of the current quark masses to the π0γγ\pi^0\rightarrow\gamma\gamma decay width at the next leading order. 2%2\% enhancement has been predicted and there is no new parameter.Comment: 9 page

    The Lyman <span class='mathrm'>α</span> and Lyman <span class='mathrm'>β</span> lines in solar coronal streamers

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    The influence of reconstruction criteria on the sensitive probes of the symmetry potential

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    Different criteria of constructing clusters and tracing back Δ\Delta resonances from the intermediate-energy neutron-rich HICs are discussed by employing the updated UrQMD transport model. It is found that both the phase-space and the coordinate-density criteria affect the single and the double neutron/proton ratios of free nucleons at small transverse momenta, but the influence becomes invisible at large transverse momenta. The effect of different methods of reconstructing freeze-out Δ\Deltas on the Δ0/Δ++\Delta^0/\Delta^{++} ratio is strong in a large kinetic energy region.Comment: 8 pages, 7 fig

    Excitation function of nucleon and pion elliptic flow in relativistic heavy-ion collisions

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    Within a relativistic transport (ART) model for heavy-ion collisions, we show that the recently observed characteristic change from out-of-plane to in-plane elliptic flow of protons in mid-central Au+Au collisions as the incident energy increases is consistent with the calculated results using a stiff nuclear equation of state (K=380 MeV). We have also studied the elliptic flow of pions and the transverse momentum dependence of both the nucleon and pion elliptic flow in order to gain further insight about the collision dynamics.Comment: 8 pages, 2 figure

    Correlations of chaotic eigenfunctions: a semiclassical analysis

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    We derive a semiclassical expression for an energy smoothed autocorrelation function defined on a group of eigenstates of the Schr\"odinger equation. The system we considered is an energy-conserved Hamiltonian system possessing time-invariant symmetry. The energy smoothed autocorrelation function is expressed as a sum of three terms. The first one is analogous to Berry's conjecture, which is a Bessel function of the zeroth order. The second and the third terms are trace formulae made from special trajectories. The second term is found to be direction dependent in the case of spacing averaging, which agrees qualitatively with previous numerical observations in high-lying eigenstates of a chaotic billiard.Comment: Revtex, 13 pages, 1 postscript figur

    τρππν\tau\to\rho\pi\pi\nu decays

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    Effective chiral theory of mesons is applied to study the four decay modes of τρππν\tau\to\rho\pi\pi\nu. Theoretical values of the branching ratios are in agreement with the data. The theory predicts that the a1a_{1} resonance plays a dominant role in these decays. There is no new parameter in this study.Comment: 12 pages and one figur