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The K^*_0(800) scalar resonance from Roy-Steiner representations of pi K scattering

S. Descotes-Genon·B. Moussallam
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Abstract

We discuss the existence of the light scalar meson K^*_0(800) (also called kappa) in a rigorous way, by showing the presence of a pole in the pi K --> pi K amplitude on the second Riemann sheet. For this purpose, we study the domain of validity of two classes of Roy-Steiner representations in the complex energy plane. We prove that one of them is valid in a region sufficiently broad in the imaginary direction. From this representation, we compute the l=0 partial wave in the complex plane with neither additional approximation nor model dependence, relying only on experimental data. A scalar resonance with strangeness S=1 is found with the following mass and width: E_kappa = 658 \pm 13 MeV and Gamma_kappa = 557 \pm 24 MeV.

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S. Descotes-Genon, B. Moussallam. 2006-08-25. The K^*_0(800) scalar resonance from Roy-Steiner representations of pi K scattering. https://doi.org/10.1140/epjc%2Fs10052-006-0036-2

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