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Mass and width of the lowest resonance in QCD
Irinel Caprini, Gilberto Colangelo, Heinrich Leutwyler
We demonstrate that near the threshold, the pi pi scattering amplitude contains a pole with the quantum numbers of the vacuum - commonly referred to as the sigma - and determine it…
Theoretical Aspects of the Pion-Pion Interaction
Irinel Caprini, Gilberto Colangelo, Heinrich Leutwyler
We give a brief review of the theoretical description of low energy pion-pion scattering by the combined use of Chiral Perturbation Theory and Roy equations, an update of the Regge…
On the infrared freezing of perturbative QCD in the Minkowskian region
Irinel Caprini, Jan Fischer
The infrared freezing of observables is known to hold at fixed orders of perturbative QCD if the Minkowskian quantities are defined through the analytic continuation from the Eucli…
Bounds on the slope and the curvature of the scalar Kπform factor at zero momentum transfer
Claude Bourrely, Irinel Caprini
We derive and calculate unitarity bounds on the slope and curvature of the strangeness-changing scalar form factor at zero momentum transfer, using low-energy constraints and Watso…