ar X iv : h ep - p h / 02 12 38 3 v 1 2 9 D ec 2 00 2 1 The Present Status on σ and κ Meson Properties Muneyuki

The recent experimental data of both ππ/Kπ scattering and production processes, suggesting the existence of scalar σ and κ mesons, are reviewed. In many ππ/Kπ production processes the direct effects of their productions are observed, while they are, because of chiral symmetry, hidden in scattering processes, and now σ(500∼600) and κ(800∼900) are considered to be confirmed experimentally. The recent criticism on our method of analyses, which is based on the long believed prejudice of universal ππ/Kπ phase through scattering and production amplitudes, is explained not to be valid. The iso-singlet scalar σ meson was introduced theoretically in the linear σ model 1) , and its existence was first suggested in one-boson-exchange potential model 2) of nuclear forces. The importance of σ was stressed 3), 4) in relation with dynam-ical chiral symmetry breaking of QCD. However, its existence had been neglected phenomenologically for many years, being based on the negative results 5) of ππ scattering phase shift analyses. Recently the ππ phase shift 6) was reanalyzed by many groups 7) including ours 8) and the existence of light σ(450-600) was strongly suggested. The result of the previous analysis with no σ existence was pointed out 9) to be not correct, since in this analysis 5) there is no consideration on the cancellation mechanism between σ amplitude and non-resonant ππ amplitude, which is guaranteed by chiral symmetry. On the other hand, it is remarkable that, in contrast with the spectra of ππ scattering, the clear peak structure has been observed in mass region of m ππ ∼ 500 MeV in the various ππ production processes, such as J/ψ → ωππ, 10)-12) p¯ p → 3π 0 , 13), 14) D + → π + π − π − 15) and τ − → π − π 0 π 0 ν τ , 16) and this structure is shown to be well reproduced by the Breit-Wigner amplitude of σ meson. Thus, presently firm evidences 17) of σ seem to be accumulated, and the column of σ in particle data group table is corrected as " f 0 (600) or σ " in the newest'02 18) edition in place of f 0 (400–1200) or σ in the '96–'00 editions. There are now hot controversies on the existence of I = 1/2 scalar κ meson, to be assigned as a member of σ nonet. Reanalyses 19), 20) of Kπ scattering phase shift 21) suggest existence …