Narrow Results

Data of the Crystal Barrel and L3 collaborations clarified essentially the situation in the 2⁺⁺ sector in the mass region up to 2400 MeV, demonstrating the linearity of (n, M²) trajectories, where n is the radial quantum number of a quark–antiquark state with mass M. We discuss these data and show that there exists a superfluous state for the (n, M²) trajectories: a broad resonance f₂(2000). We pay special attention to the reactions in the mass region 1990–2400 MeV where, together with f₂(2000), four relatively narrow resonances are seen: f₂(1920), f₂(2020), f₂(2240), f₂(2300). We analyze the branching ratios of all these resonances and show that only the decay couplings of the broad state f₂(2000) → π⁰π⁰, ηη, ηη′ satisfy relations inherent in the glueball decay.

The masses and decay constants of the light tensor mesons were calculated with quantum numbers $J^P=2^{+}$ in the framework of the QCD sum rules in the standard model. The non perturbative contributions up to dimension-5 are considered as important terms of the operator product expansion.