Paper detail

Precise determination of the f0(500) and f0(980) parameters in dispersive analysis of the pipi data

We review the use of new and precise dispersive equations, which also implement crossing symmetry, in order to shed further light on the long-standing puzzle in the parameters of the f0(500), as well as the f0(980). This puzzle is finally being settled thanks to several analyses carried out during the last years. In this talk we show how our very recent dispersive data analysis allowed for a precise and model independent determination of the amplitudes for the S,P,D and F waves. In particular, we show how the analytic continuation of once subtracted dispersion relations for the S0 wave to the complex energy plane leads to very precise results for the f0(500) pole: sqrt(s)_pole = 457^(+14)_(-13) - i 279^(+11)_(-7) MeV and for the f0(980) pole: sqrt(s)_pole = 996+/-7 - i 25^(+10)_(-6) MeV. We also comment on how these results have been already used for other practical applications, including a refit of a previous model to the pipi S-wave amplitudes below 1000 MeV, which improves its consistency with the poles found with the dispersive approach.