The updated SM prediction for the muon anomalous magnetic moment is 116592033(62)×10^{-11}, showing no tension with the experimental average of 38(63)×10^{-11}.
The pion-pion scattering amplitude. IV: Improved analysis with once subtracted Roy-like equations up to 1100 MeV
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abstract
We improve our description of pion-pion scattering data by imposing additional requirements to our previous fits, in the form of once-subtracted Roy-like equations, while extending our analysis up to 1100 MeV. We provide simple and ready to use parametrizations of the amplitude. In addition, we present a detailed description and derivation of these once-subtracted dispersion relations that, in the 450 to 1100 MeV region, provide an additional constraint which is much stronger than our previous requirements of Forward Dispersion Relations and standard Roy equations. The ensuing constrained amplitudes describe the existing data with rather small uncertainties in the whole region from threshold up to 1100 MeV, while satisfying very stringent dispersive constraints. For the S0 wave, this requires an improved matching of the low and high energy parametrizations. Also for this wave we have considered the latest low energy Kl4 decay results, including their isospin violation correction, and we have removed some controversial data points. These changes on the data translate into better determinations of threshold and subthreshold parameters which remove almost all disagreement with previous Chiral Perturbation Theory and Roy equation calculations below 800 MeV. Finally, our results favor the dip structure of the S0 inelasticity around the controversial 1000 MeV region.
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hep-ph 7representative citing papers
Kinetic mixing terms are introduced in the parity-doublet model to reproduce the empirical axial charge g_A ≈ 1.28 of the nucleon along with masses of the nucleon and N*(1535).
Including ππ final-state interactions in large-Nc ChPT improves agreement with η′ → η ππ data and yields Dalitz parameters a = -0.085(18)stat(4)syst, b = -0.081(10)stat(6)syst, d = -0.045(6)stat(8)syst.
CP asymmetries for B+ to pi+ pi0, D+ to pi+ pi0, and K+ to pi+ pi0 are estimated in the Standard Model at roughly 3 times 10 to the -3, 10 to the -5, and 10 to the -6 using a unified formalism for isospin violation.
Pedagogical review explaining how causality implies analyticity and its use in scattering amplitudes, form factors, and resonance extraction in hadronic physics.
The Standard Model value for the muon anomalous magnetic moment is 116591810(43)×10^{-11}, 3.7σ below the Brookhaven experimental measurement.
A hadronic approach based on dispersion relations and meson dominance achieves a successful description of lattice QCD data for gravitational form factors of pions and nucleons.
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Particle seismology: mechanical and gravitational properties from parton-hadron duality
A hadronic approach based on dispersion relations and meson dominance achieves a successful description of lattice QCD data for gravitational form factors of pions and nucleons.