Quark and glue spectroscopy of scalars and pseudoscalars in SU(3) flavor limit

Within the framework of the generalized linear sigma model with glueballs recently proposed,[Formula: see text] we study the schematic spectroscopy of scalar and pseudoscalar mesons in the SU(3) flavor limit and explore their quark and glue contents. In this framework, for both scalars and pseudoscalars, the two octet physical states are admixtures of quark–antiquark and four-quark components, and the three singlet states contain quark–antiquark, four-quark and glue components. We identify the two scalar octets with [Formula: see text] and [Formula: see text] and the two pseudoscalar octets with [Formula: see text] and [Formula: see text]. We show that, as expected, the light pseudoscalar octet is made dominantly of quark–antiquarks whereas the light scalar octet has a reversed substructure with a dominant four-quark component. The case of singlets is more complex due to surplus of states up to around 2 GeV. We consider all 35 permutations for identifying the three pseudoscalar singlets of our model with three of the seven experimental candidates. Our numerical simulation unambiguously identifies the lightest and the heaviest pseudoscalar singlets with [Formula: see text] and [Formula: see text], respectively, and favors the identification of the middle singlet with either [Formula: see text] or [Formula: see text] (or, to a lesser extent, with [Formula: see text]) and thereby allows a probe of their substructures. We then estimate the quark and glue components and find that the three pseudoscalar singlets (from lightest to heaviest) are mainly of quark–antiquark, four-quark and glue substructure, while the corresponding three scalar singlets (from lightest to heaviest) are of four-quark, quark–antiquark and glue contents. The masses of pure pseudoscalar and scalar glueballs are estimated around 2.0 and 1.6 GeV, respectively.

Resonance contribution of scalar color octet to tt̄ production at the LHC in the minimal four-color quark–lepton symmetry model

The scalar color octet contribution to the resonance [Formula: see text]-pair production at the LHC is calculated and analyzed by taking into account the one-loop effective two-gluon vertex. It is shown that this contribution from the scalar color octet [Formula: see text] predicted by the minimal model with the four-color quark–lepton symmetry is for [Formula: see text] = 13 TeV of about a few percent for 750 [Formula: see text] 1800 GeV and can exceed 10% for 400 [Formula: see text] 750 GeV. It is also pointed out that the search for the scalar octet [Formula: see text] as the resonance in the dijet mass spectra seems to be difficult because of the smallness of its one-loop effective two-gluon interaction.