Nonet Classification of Scalar/Isoscalar Resonances below 1900 MeV: the Existence of an Extra Scalar State in the Region 1200-1600 MeV

Abstract

A classification of the $I{J}^{PC}=00^{++}$ mesons is performed on the basis of the K-matrix analysis of meson spectra in the reactions: (i) GAMS data on $\pi p\to {\pi }^0{\pi }^{0}n$, $\eta \eta n$, $\eta {\eta }^{\prime }n$; (ii) Crystal Barrel data on $p\bar{p}(atrest)\to {\pi }^0{\pi }^0{\pi }^0$, ${\pi }^0{\pi }^0\eta$, ${\pi }^0\eta \eta$; (iii) CERN-Münich data on $\pi p\to {\pi }^{+}{\pi }^{-}n$; (iiii) BNL data on $\pi N\to K\bar{K}N$. The analysis points to the existence of four comparatively narrow scalar resonances which correspond to the following poles of the scattering amplitude (in MeV): $(1015\pm 15)-i(43\pm 8)$, $(1300\pm 20)-i(120\pm 20)$, $(1499\pm 8)-i(65\pm 10)$ and $(1780\pm 30)-i(125\pm 70)$. The scattering amplitude also has a fifth pole $f_0(1530_{-250}^{+90})$ at the complex mass $(1530_{-250}^{+90})-i(560\pm 140)$. The masses of the K-matrix poles (bare states) are at $720\pm 100$ MeV, $1230\pm 50$ MeV, $1260\pm 30$ MeV, $1600\pm 50$ MeV and $1810\pm 30$ MeV. The quark content of the bare states is analyzed using the values of their couplings to the $\pi \pi$, $K\bar{K}$, $\eta \eta$ and $\eta {\eta }^{\prime }$. It is shown that one of the bare states in the mass region 1200-1600 MeV is superfluous for the $q\bar{q}$ classification and should be considered as the lightest glueball.

Comments: LaTex 26 pages and 8 figures