We perform the K-matrix analysis of meson partial waves with IJ P C = 00 ++ , 10 ++ , 02 ++ , 12 ++ basing on GAMS data on π − p → π 0 π 0 n, ηηn, ηη ′ n together with BNL data on π − p → K Kn and Crystal Barrel data on pp(at rest) → π 0 π 0 π 0 , π 0 ηη, π 0 π 0 η. The positions of the amplitude poles (physical resonances) are determined as well as the positions of the K-matrix poles (bare states) and the values of bare state couplings to two-meson channels. Nonet classification of the determined bare states is discussed.

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A classification of the IJ P C = 00 ++ mesons is performed on the basis of the Kmatrix analysis of meson spectra in the reactions: (i) GAMS data on πp → π 0 π 0 n, ηηn, ηη ′ n [1, 2, 3]; (ii) Crystal Barrel data on pp (at rest) → π 0 π 0 π 0 , π 0 π 0 η, π 0 ηη [4,5]; (iii) CERN-Münich data on πp → π + π − n [6]; (iiii) BNL data on πN → KKN [7]. 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 ± 15) − i(43 ± 8), (1300 ± 20) − i(120 ± 20), (1499 ± 8) − i(65 ± 10) and (1780±30)−i(125±70). The scattering amplitude also has a fifth pole f 0 (1530 +90 −250 ) at the complex mass (1530 +90 −250 ) − i(560 ± 140). The masses of the K-matrix poles (bare states) are at 720 ± 100 MeV, 1230 ± 50 MeV, 1260 ± 30 MeV, 1600 ± 50 MeV and 1810 ± 30 MeV. The quark content of the bare states is analyzed using the values of their couplings to the ππ, KK, ηη and ηη ′ . It is shown that one of the bare states in the mass region 1200-1600 MeV is superfluous for the qq classification and should be considered as the lightest glueball. The search for and classification of scalar/isoscalar IJ P C = 00 ++ states is the direct and possibly the only way for identification of the lightest scalar glueball. In refs. [8,9] the K-matrix analysis of the 00 ++ -wave was performed in the mass region up to 1550 MeV, where four scalar resonances (the T-matrix poles at the complex masses: (1008 ± 10) −i(43 ±5), (1290 ±25) −i(120 ±15), (1497 ±6) −i(61 ±5), (1430 ±150) −i(600 ±100), in MeV) were found. Correspondingly, four bare states were determined: the lightest bare state with mass 750 ± 100 MeV is dominantly ss, while three other states, with masses 1240 ± 30 MeV, 1280 ± 30 MeV and 1615 ± 50 MeV, do not contain a large ss component. One of these states, either the state with mass 1240 MeV or the state with mass 1280 MeV, is a natural qq-partner of the lightest bare state. For the other two states two scenarios arose in ref.[9]:(a) both these states are qq mesons; then, in the region 1550-1900 MeV, two ss-rich states exist as the nonet partners of the low-lying 00 ++ -mesons;(b) in the region 1550-1900 MeV there is only one ss-rich 00 ++ state; then one of the low-lying states is exotic, probably the lightest glueball.To resolve these alternatives, the spectra in KK, ηη and ηη ′ channels need to be investigated in the region 1550-1900 MeV: the existence of a strange component in these mesons favours a search for the ss-rich states. The ηη and ηη ′ spectra obtained by the GAMS collaboration [2,3] give a good opportunity for this study. The aim here is to extend the analysis of the 00 ++ -wave to a mass of 1900 MeV, including the ηη and ηη ′ GAMS spectra into the simultaneous fitting procedure. The main purpose is to identify the ss-rich states: the analysis of the π 0 π 0 and π + π − spectra from refs. [9,10] definitely indicates that in the region 1550-1900 MeV there are no 00 ++ resonances with a significant ππ branching ratio...