Identification of the glueballs and the scalar meson nonet of lowest mass

Abstract

We discuss the theoretical expectations and phenomenological evidence for the lightest glueballs and the members of the meson nonet with quantum numbers J P C = 0 ++ . We reconsider the recent evidence for candidate states with masses below ∼1700 MeV, but include also the results from earlier phase-shift analyses. Arguments are presented to classify the scalars f 0 (980) and f 0 (1500) as members of the 0 ++ nonet, with a mixing rather similar to that of the pseudoscalars η and η. The S-wave states called f 0 (400 − 1200) and f 0 (1370) are considered as different signals from a single broad resonance, which we take to be the lowest-lying 0 ++ glueball. This state together with η(1440) and f J (1710) with spin J = 2 form the basic triplet of binary gluonic bound states. We argue that these hypotheses are consistent with what can be expected theoretically.

Gluonia, scalar and hybrid mesons in QCD

“…which suggests a huge OZI violation and seriously questions the validity of the lattice results in the quenched approximation. Similar conclusions have been reached in [28][29][30]. For testing the above result, one should evaluate on the lattice, the decay mixing 3-point function V (0) responsible for such decays using dynamical fermions.…”

“…The huge coupling of the f 0 toKK comes from the large mixing with the σ. For this reason, the f 0 can have a large singlet component, as also suggested from independent analysis [28,29]. Extending the previous J/ψ → γ + X analysis into the case of the φ, one obtains the new result within this scheme [40]:…”

“…As already mentioned previously, this region is quite complicated due to the proliferation of states. Many scenarios have been proposed in the literature for trying to interpret this region [41,17,28,29,38]. However, one needs to clarify and to confirm the data [42] for selecting these different interpretations.…”

Vector and scalar mesons’ mixing from QCD sum rules

“…However, we can conclude that the f 0 (500) has both gluonic and qq components because this state emerges from the mixed correlator (4.2), and our smallmixing result suggests that the relative proportion of one of component may dominate the other. In some previous analyses the relative proportion of gluonic components are more prominent thanqq (see e.g., [31,32,[73][74][75]) , while in other approaches it is the opposite (see e.g., [45,76]).…”

Exclusive channels in γγ reactions: Light at the end of the tunnel?

“…This notwithstanding, the f 0 (1500) and f J (1710) have been proposed as glueball candidates, in keeping with the lattice expectations we have just discussed, for their undressed masses. Very recently, Minkowski and Ochs [31] have proposed that it is the broad f 0 (400 − 1200) that is largely gluish. Since any of these states sits amongst the qq scalars they inevitably mix with them, whether at the bare or dressed levels.…”