The σ and from scatterings data

Abstract: We systematically reconsider, within an improved “analytic K-matrix model”, the extraction of the and masses, widths and hadronic couplings using new data on ππ phase shift below 390 MeV and different sets of scatterings data from 400 MeV to 1.4 GeV. Our results are summarized in Tables 1, 2 and 5. In units of MeV, the complex poles are: and , which are comparable with some recent high-precision determinations and with PDG values. Besides some other results, we find: which confirms a sizeable coupling found earlier, and which disfavours a large ππ molecule or four-quark component of the σ, while its broad ππ width (relative to the one of the ρ-meson) cannot be explained within a scenario. The narrow ππ width of the and the large value: , excludes its pure content. A significant gluonium component eventually mixed with appears to be necessary for evading the previous difficulties. [Copyright &y& Elsevier]