Two-pion emission decays of negative parity singly heavy baryons

We investigate two-pion emission decays of singly charmed and bottom baryons, focusing on ΛQ^*(1P) and ΞQ^*(1P) with $Q=c$ (charm) or b (bottom) quarks and JP=1/2⁻,3/2⁻, belonging to antisymmetric flavor triplet 3̄F. Our analysis encompasses both sequential processes, involving intermediate states belonging to symmetric flavor sextet 6F such as ΣQ(1S) and ΞQ⁽1S) respectively with JP=1/2⁺,3/2⁺, derived from the chiral quark model, and direct process crucial for comparison with experimental data, whose coupling constants estimated using the chiral-partner scheme. We also incorporate the convolution of the parent particle's mass for the Dalitz plot, enabling a more realistic comparison with experimental data. We scrutinize the Dalitz plots of these negative parity states in light of recent Belle measurements for Λc(2625)⁺. Our findings support the assignment of Λc(2625)⁺ as the λ-mode excitation with JP=3/2⁻ in the quark model, deduced from the the Λcπ invariant mass distribution, and we then give predictions for other cases, including the ΞQ^* decays. The observed asymmetry in the ππ invariant mass distribution underscores the important role of the direct process, reflecting the chiral-partner structure in the heavy baryon sector. It is evident that the presence of the direct process is not significant in the three-body decays unless the S-wave resonance contribution is suppressed. We suggest further experimental verification to test our predictions and get more insights into the structure of heavy baryons.