Dispersive analysis with ρ-ω mixing produces a two-parameter fit describing BESIII data on the J/ψ→π⁰γ* form factor from 0 to 2.8 GeV and extracts a (62 ± 21)° relative phase between strong and electromagnetic modes.
N_f Dependence of the Quark Condensate from a Chiral Sum Rule
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abstract
How fast does the quark condensate in QCD-like theories vary as a function of $N_f$ is inferred from real QCD using chiral perturbation theory at order one-loop. A sum rule is derived for the single relevant chiral coupling-constant, $L_6$. A model independent lower bound is obtained. The spectral function satisfies a Weinberg-type superconvergence relation. It is discussed how this, together with chiral constraints allows a solid evaluation of $L_6$, based on experimental $\pi\pi-K\bar K$ S-wave T-matrix input. The resulting value of $L_6$ is compatible with a strong $N_f$ dependence possibly suggestive of the proximity of a chiral phase transition
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Pedagogical review explaining how causality implies analyticity and its use in scattering amplitudes, form factors, and resonance extraction in hadronic physics.
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Dispersive analysis of the $J/\psi\to\pi^0 \gamma^\ast$ transition form factor with $\rho$-$\omega$ mixing effects
Dispersive analysis with ρ-ω mixing produces a two-parameter fit describing BESIII data on the J/ψ→π⁰γ* form factor from 0 to 2.8 GeV and extracts a (62 ± 21)° relative phase between strong and electromagnetic modes.
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Dispersion relations: foundations
Pedagogical review explaining how causality implies analyticity and its use in scattering amplitudes, form factors, and resonance extraction in hadronic physics.