The sigma and f_0(980) from Ke4 + pi-pi scatterings data

Abstract : We systematically reconsider, within an improved "analytic K-matrix model", the extraction of the sigma = f_0(600) and f_0(980) masses, widths and hadronic couplings using new Ke4 = 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 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_sigma=452(12) - i 260(15) and M_f=981(34) -i 18(11), which are comparable with some recent high-precision determinations and with PDG values. Besides some other results, we find: |g_{sigma K+K-}|/|g_{sigma pi+pi-}|=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 \bar qq scenario. The narrow pi-pi width of the f_0(980) and the large value: |g_{f K+K-}|/|g_{f pi+pi-}|=2.59(1.34), excludes its pure (\bar uu+\bar dd) content. A significant gluonium component eventually mixed with \bar qq appears to be necessary for evading the previous difficulties.
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Contributeur : Logiciel Aigle <>
Soumis le : mercredi 17 février 2010 - 11:48:55
Dernière modification le : mardi 17 janvier 2017 - 15:36:01




Gerard Mennessier, Stephan Narison, X. -G. Wang. The sigma and f_0(980) from Ke4 + pi-pi scatterings data. Physics Letters B, Elsevier, 2010, 688 (1), pp.59-66. <10.1016/j.physletb.2010.03.031>. <hal-00457346>



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