Narrow Results

We use the method of QCD sum rules to estimate the masses of the charm baryon, ${\mathrm{\Lambda }}_c^{+}$, bottom baryon ${\mathrm{\Lambda }}_b^0$, strange baryon ${\mathrm{\Lambda }}_s^0$ and compare them to their experimental values.

Charmed dibaryon states with the spin-parity $J^{\pi }=0^{+},1^{+}$, and $2^{+}$ are predicted for the two-body $Y_{c}N$ ($={\mathrm{\Lambda }}_c$, ${\mathrm{\Sigma }}_c$, or ${\mathrm{\Sigma }}_c^{\ast }$) systems. We employ the complex scaling method for the coupled channel Hamiltonian with the $Y_{c}N$-CTNN potentials, which were proposed in our previous study. We find four sharp resonance states near the ${\mathrm{\Sigma }}_{c}N$ and ${\mathrm{\Sigma }}_c^{\ast }N$ thresholds. From the analysis of the binding energies of partial channel systems, we conclude that these resonance states are Feshbach resonances. We compare the results with the $Y_{c}N$ resonance states in the heavy quark limit, where the ${\mathrm{\Sigma }}_{c}N$ and ${\mathrm{\Sigma }}_c^{\ast }N$ thresholds are degenerate, and find that they form two pairs of the heavy-quark doublets in agreement with the heavy quark spin symmetry.

We report an experimental determination of the isospin of ${\mathrm{\Lambda }}_c/{\mathrm{\Sigma }}_c{\left(2765\right)}^{+}$ using 980 fb⁻¹ data in the e⁺e⁻ annihilation around $\sqrt{s}=10.6\text{GeV}$ collected by the Belle detector located at the KEKB collider. The isospin partners are searched for in the ${\mathrm{\Sigma }}_c{\left(2455\right)}^{++/0}{\pi }^0$ channels, and no evidence was obtained. Thus the isospin is determined to be zero, and the particle is established to be a Λ_c.