The σ and f0(980) from Ke4 ⊕ ππ scatterings data

We systematically reconsider, within an improved analytic K-matrix model, the extraction of the sigma equivalent to f(0)(600) and f(0)(980) masses, widths and hadronic couplings using new K-e4 equivalent to K -> pi pi e nu(e) data on pi pi phase shift below 390 MeV and different sets of pi pi -> pi pi/K (K) over bar 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: M-o = 452(12) - i260(15) and M-f = 981(34) - i18(11), which are comparable with some recent high-precision determinations and with PDG values. Besides some other results, we find: vertical bar g sigma(K+K-)vertical bar/vertical bar g(sigma pi) (+) (pi-) vertical bar = 0.37(6) which confirms a sizeable g(sigma K+K)- coupling found earlier, and which disfavours a large pi pi molecule or four-quark component of the sigma, while its broad pi pi width (relative to the one of the rho-meson) cannot be explained within a q (q) over bar scenario. The narrow pi pi width of the f(0)(980) and the large value: vertical bar g(fK+K-)vertical bar/vertical bar g(f pi+pi-)vertical bar = 2.59(1.34), excludes its pure ((u) over baru + (d) over bard) content. A significant gluonium component eventually mixed with (q) over barq appears to be necessary for evading the previous difficulties. (C) 2010 Elsevier B.V. All rights reserved.