Predictions for feed-down enhancements at the $\hat{I}{›}_c\bar{D}$ and $\hat{I}{›}_c{\bar{D}}^{\ast }$ thresholds via the triangle and box singularities

Abstract

We demonstrate that triangle singularity (TS) and box singularity (BS) mechanisms can produce unique narrow enhancements at the $\hat{I}{›}_c\bar{D}$ and $\hat{I}{›}_c{\bar{D}}^{\ast }$ thresholds in the invariant mass spectra of $J/\ddot{I}ˆp$ and $J/\ddot{I}ˆp\ddot{I}€$, respectively. Taking into account that such mechanisms only depend on the initial $\hat{I}{\pounds }_c^{(\ast )}{\bar{D}}^{(\ast )}$ interactions near threshold within the TS or BS kinematic regimes, the $\hat{I}{›}_c\bar{D}$ and $\hat{I}{›}_c{\bar{D}}^{\ast }$ threshold enhancements can be regarded as a feed-down phenomenon originated from both the heavier pentaquark decays and the $\hat{I}{\pounds }_c^{(\ast )}{\bar{D}}^{(\ast )}$ scatterings from the continuum. A search for these structures in the $J/\ddot{I}ˆp$ and $J/\ddot{I}ˆp\ddot{I}€$ spectra in both exclusive and semi-inclusive processes will provide a smoking-gun evidence for the hadronic molecule nature of those observed pentaquarks and clarify the role played by the TS and BS in the near-threshold dynamics.

Revtex, 6 pages, 5 figures; Comments are welcome