Uncertainty estimates of the σ-pole determination by Padé approximants

We discuss the determination of the f0(500) (or σ) resonance by analytic continuation through Padé approximants of the ππ-scattering amplitude from the physical region to the pole in the complex energy plane. The aim is to analyze the uncertainties of the method, having in view the fact that analytic continuation is an ill-posed problem in the sense of Hadamard. Using as input a class of admissible parametrizations of the scalar-isoscalar ππ partial wave, which satisfy with great accuracy the same set of dispersive constraints, we find that the Roy-type integral representations lead to almost identical pole positions for all of them, while the predictions of the Padé approximants have a larger spread, being sensitive to features of the input parametrization that are not controlled by the dispersive constraints. Our conservative conclusion is that the σ-pole determination by Padé approximants is consistent with the prediction of Roy-type equations, but has an uncertainty almost a factor of 2 larger.

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11 pages, 13 figures

11.55.Bq
11.55.Fv
14.40.Be
Pade approximation
pi pi: scattering
dispersion
partial wave
pole
parametrization
integral equations

References(0)

Figures(13)

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