On the mass, width and coupling constants of the f0(980)

Abstract

Using the pole approach we determine the mass and width of the $f_0(980)$; in particular, we analyze the possibility that two nearby poles are associated to it. We restrict our analysis to a neighborhood of the resonance, using $\pi \pi$ data for the phase shift and inelasticity, and the invariant mass spectrum of the $J/\psi \to \varphi \pi \pi ,\varphi K\bar{K}$ decays. The formalism we use is based on unitarity and a generalized version of the Breit-Wigner parameterization. We find that a single pole describes the $f_0(980)$, the precise position depending upon the $\pi \pi$ data used. As a byproduct, values for the $g_{f_0\pi \pi }$ and $g_{f_{0}K\bar{K}}$ coupling constants are obtained.

Comments: 18 pages, 2 figures. A new analysis including the latest pi-pi phase shift data is performed. To be published in Eur. Phys. J. C