$T_{bc\bar{s}}$ states in the process ${\rm Y}\to D^{-}{\bar{B}}^0{D}_s^{+}$

Abstract

We perform a theoretical study of the decay process ${\rm Y}\to D^{-}{\bar{B}}^0{D}_s^{+}$ in search of the doubly heavy tetraquark states $T_{bc\bar{s}}$ with quark content $bc\bar{s}\bar{d}$. These $T_{bc\bar{s}}$ states are assumed to be dynamically generated molecular states from the S-wave interactions between ${\bar{B}}_s^{(\ast )0}{D}^{(\ast )+}$ and ${\bar{B}}^{(\ast )0}{D}_s^{(\ast )+}$ meson pairs. Based on the total angular momentum and the type of the constituent mesons (pseudoscalars $P$ or vectors $V$), they are labeled as $T_{bc\bar{s}}^{0,PP}$, $T_{bc\bar{s}}^{0,VV}$, and $T_{bc\bar{s}}^{2,VV}$, respectively. The ${\bar{B}}^0{D}_s^{+}$ invariant mass distribution for this decay is calculated using current algebra, incorporating contributions from $T_{bc\bar{s}}$ states arising from final-state interactions. Our results reveal a clear peak structure in the $7415-7425$ MeV region, which is attributed to the $T_{bc\bar{s}}^{2,VV}$ state. Additionally, a distinct dip structure appears near the ${\bar{B}}^{\ast 0}{D}_s^{\ast +}$ threshold, characteristic of the $T_{bc\bar{s}}^{2,VV}$ as a hadronic molecular state. A near-threshold enhancement associated with the $T_{bc\bar{s}}^{0,PP}$ state and a dip arising from the $T_{bc\bar{s}}^{0,VV}$ state are also identified, though the manifestation of these features depends sensitively on model parameter fine-tuning. Therefore, with increased experimental statistics, the decay channel ${\rm Y}\to D^{-}{\bar{B}}^0{D}_s^{+}$ offers a promising avenue for discovering and characterizing the $T_{bc\bar{s}}$ states.

Comments: 25 pages, 5 figures, 2 tables, suggestions and comments welcome