Nonet Classification of Scalar/Isoscalar Resonances in the Mass Region below 1900 MeV: Observation of the Lightest Scalar Glueball

We summarize the results of the investigation of the $IJ^{PC}=00^{++}$ wave which is devoted to the search for the lightest scalar glueball. In the framework of the K-matrix formalism, the $q\bar q$-nonet classification of the scalar/isoscalar states is performed in the mass region below 1900 MeV basing on the following data: GAMS data for $\pi^-p\to\pi^0\pi^0n$, $\eta\eta n$, $\eta\eta'n$; CERN-M\"unich data for $\pi^-p\to\pi^+\pi^-n$; Crystal Barrel data for $p\bar p\to\pi^0\pi^0\pi^0$, $\pi^0\pi^0\eta$, $\pi^0\eta\eta$; BNL data for $\pi\pi\to K\overline K$. It is shown the existence of an extra state for $q\bar q$ classification: this state is a good candidate for the lightest scalar glueball. Analysis of the glueball/$q\bar q$ mixing shows that the glueball state has mainly dispersed over three real resonances: $f_0(1300)$, $f_0(1500)$ and $f_0(1530^{+90}_{-250})$. The broad resonance with complex mass $m=1530^{+90}_{-250}-i(560\pm 140)$ MeV is descendant of the pure glueball. The restored mass of the pure glueball is equal to 1695 MeV. This value agrees well with the results of lattice gluodynamics.Comment: LaTex, 5 pages and 7 figures. Talk given by V.V.Anisovich at LEAP96, Dinkelsbuhl, German

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

A classification of the $IJ^{PC}=00^{++}$ mesons is performed on the basis of the K-matrix analysis of meson spectra in the reactions: (i) GAMS data on $\pi p\to \pi^0\pi^0 n$, $\eta\eta n$, $\eta\eta' n$; (ii) Crystal Barrel data on $p\bar p~(at~rest)\to \pi^0\pi^0\pi^0$, $\pi^0\pi^0\eta$, $\pi^0\eta\eta$; (iii) CERN-M\"unich 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 $f_0(1530^{+90}_{-250})$ at the complex mass $(1530^{+90}_{-250}) - i(560\pm 140)$. 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 $\eta\eta'$. 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.Comment: LaTex 26 pages and 8 figure

ππ\pi\pi scattering S wave from the data on the reaction π−p→π0π0n\pi^-p\to\pi^0\pi^0n

The results of the recent experiments on the reaction $\pi^-p\to\pi^0\pi^0n$ performed at KEK, BNL, IHEP, and CERN are analyzed in detail. For the I=0 $\pi\pi$ S wave phase shift $\delta^0_0$ and inelasticity $\eta^0_0$ a new set of data is obtained. Difficulties emerging when using the physical solutions for the $\pi^0\pi^0$ S and D wave amplitudes extracted with the partial wave analyses are discussed. Attention is drawn to the fact that, for the $\pi^0\pi^0$ invariant mass, m, above 1 GeV, the other solutions, in principle, are found to be more preferred. For clarifying the situation and further studying the $f_0(980)$ resonance thorough experimental investigations of the reaction $\pi^-p\to\pi^0\pi^0n$ in the m region near the $K\bar K$ threshold are required.Comment: 17 pages, 5 figure

A study of the centrally produced 4pi channel in pp interactions at 450 GeV/c

The reaction pp -> pf (pi+pi-pi+pi-) ps has been studied at 450 GeV/c in an experiment designed to search for gluonic states. A spin analysis has been performed and the dPT filter applied. In addition to the well known f1(1285) there is evidence for two JPC=2-+ states called the eta2(1620) and eta2(1875) and a broad scalar called the f0(2000). The production of these states as a function of the dPT kinematical filter shows the behaviour expected for qqbar states. In contrast, there is evidence for two states at 1.45 GeV and at 1.9 GeV which do not show the behaviour observed for qqbar states.Comment: 14 pages, Latex, 3 Figure