Recently, a hadronic state named ${\eta }_1(1855)$, about 1.86 GeV, was observed in the BESIII experiment. This finding has a peculiar interest due to its exotic quantum number $J^{\mathrm{PC}}=1^{-+}$. In this paper, we examine the tetraquark interpretation for the structure of ${\eta }_1(1855)$ in the configurations of $[1_c{]}_{\overline{s}s}\otimes [1_c{]}_{\overline{q}q}$ and $[1_c{]}_{\overline{s}q}\otimes [1_c{]}_{\overline{s}q}$, and perform a mass spectrum calculation in the framework of QCD sum rules. The results show that the observed ${\eta }_1(1855)$ could be embedded into the $[1_c{]}_{\overline{s}s}\otimes [1_c{]}_{\overline{q}q}$ configuration. The possible tetraquark and hybrid decay modes are analyzed, which are critical in decoding its inner structure. In the same way, we evaluate as well the $\overline{s}s\overline{s}s$ molecular state with $1^{-+}$ quantum number and find that there might exist two such ground states.

We evaluate the light baryonium spectrum, viz. the baryon-antibaryon states, in the framework of QCD sum rules. The nonperturbative contributions up to dimension 12 are taken into account. Numerical results indicate that there might exist eight possible light baryonium states, i.e. $p-\overline{p}$, $\mathrm{\Lambda }-\overline{\mathrm{\Lambda }}$, $\mathrm{\Sigma }-\overline{\mathrm{\Sigma }}$, and $\mathrm{\Xi }-\overline{\mathrm{\Xi }}$ with quantum numbers of $0^{-+}$ and $1^{--}$. For the $\mathrm{\Lambda }-\overline{\mathrm{\Lambda }}$, $\mathrm{\Sigma }-\overline{\mathrm{\Sigma }}$, and $\mathrm{\Xi }-\overline{\mathrm{\Xi }}$ states, their masses are found above the corresponding dibaryon thresholds, while the masses of $p-\overline{p}$ states are not. The possible baryonium decay modes are analyzed, which are hopefully measurable in BESIII, BELLEII, and LHCb experiments.

Motivated by the recent experimental progress in the ${\mathrm{\Lambda }}_c$ decay that contains a neutron in the final state, we analyze the semileptonic decay ${\mathrm{\Lambda }}_c\to n\ell {\nu }_{\ell }$ in the framework of QCD sum rules. The transition form factors are analytically computed using three-point correlation functions and the Cutkosky cutting rules, which can be extrapolated into the physical region by employing the $z$-series parametrization. The branching fractions of ${\mathrm{\Lambda }}_c\to n{e}^{+}{\nu }_e$ and ${\mathrm{\Lambda }}_c\to n{\mu }^{+}{\nu }_{\mu }$ are estimated to be $(0.281\pm 0.056)\%$ and $(0.275\pm 0.055)\%$, respectively. Furthermore, we calculate as well the relevant decay asymmetry observables sensitive to new physics beyond the standard model. The numerical results of semileptonic decays ${\mathrm{\Lambda }}_c\to \mathrm{\Lambda }\ell {\nu }_{\ell }$ are also given and confronted to the latest experimental data.

We investigate the hyperon semileptonic decays within the framework of QCD sum rules. The flavor SU(3) symmetry breaking effects are analyzed via the relevant form factors and corresponding branching fractions. Employing the z-series parameterization to capture the q ² dependence of form factors, we calculate the hyperon semileptonic decay rates and confront them with the recent experimental measurements. Moreover, we calculate as well the non-standard tensor form factors, which involve certain new physics beyond the standard model.

Motivated by the newly observed resonance $X(2600)$ by BESIII Collaboration, we examine the trigluon glueball interpretation for it in the framework of QCD sum rules. We evaluate the mass spectra of the trigluon glueballs with quantum numbers $0^{-+}$ and $2^{-+}$ up to dimension 8 condensate in the operator product expansion. Our numerical results indicate that the mass of the $2^{-+}$ trigluon glueball is about $2.66\pm 0.06\mathrm{GeV}$, which is consistent with the mass of the X(2600) within the uncertainties, while $0^{-+}$ has a mass of $2.01\pm 0.14\mathrm{GeV}$. The possible decay channels of the $2^{-+}$ state are analyzed, which are crucial in decoding $X(2600)$’s internal structure and are hopefully measurable in BESIII, BEllEII, PANDA, and LHCb experiments.

Recent experimental progress on baryonic rare decays has spurred a deeper investigation on flavor-changing neutral current transitions in the baryon sector. Within the framework of QCD sum rules, we derive a complete set of form factors for the Λ c → p process in the large recoil region and use the z -series parametrization to extrapolate them across the full physical range. Employing these form factors and flavor symmetries, we compute branching fractions for the decays Λ c → p e + e − and Λ c → p μ + μ − , as well as for rare Ξ c decay modes. We examine as well the new physics effects through specific angular observables such as the lepton forward-backward asymmetry and the fraction of longitudinally polarized dileptons. Results indicate that new physics models may be testified in baryonic rare decays, with immense data collected in running and future colliders. Published by the American Physical Society 2024