Narrow Results

We study the ϕ(2170) state as a vector $\overline{s}gs$ strangeonium hybrid meson with J^PC = 1⁻⁻ by using the QCD Gaussian sum-rules method. In a two-resonance model, the relative resonance strength of the ϕ(2170) state was found to be less than 5% that of a heavier 2.9 GeV state, which disfavors the hybrid interpretation of the ϕ(2170).

We use the method of QCD sum rules to study the mass spectrum of the Ξ_b(6227) and Σ_b(6097) recently observed by LHCb. We also use the method of light-cone sum rules to study their decay properties. Our results suggest that they can be well interpreted as P-wave bottom baryons with J^P = 3/2⁻.

We use the method of QCD sum rules to study $ss\overline{s}\overline{s}$ tetraquark states of J^PC = 1⁻⁻ and J^PC = 1⁺⁻. Our results suggest that the Y (2175) can be interpreted as an $ss\overline{s}\overline{s}$ state of J^PC = 1⁻⁻, and it has a partner state, whose mass is ${71}_{-48}^{+172}$ MeV larger.

The QCD sum rule method is applied to the Θ⁺ pentaquark with quantum numbers . It is found that the sum rule gives positive evidence for the state, while we cannot extract any evidence for the state.

We study the neutron electric dipole moment in the presence of the CP-violating operators up to the dimension five in terms of the QCD sum rules. By using input parameters obtained from the lattice simulation, we derive a conservative limit for the contributions of the CP violating operators.