Five-flavor molecular pentaquarks in the $Ξ_b^{(\prime,\,*)} \bar D^{(*)}$ and $Ξ_c^{(\prime,\,*)} B^{(*)}$ systems

Abstract: The discovery of hidden-charm pentaquarks and open-flavor tetraquarks motivates the search for even more exotic hadron configurations. In this work, we investigate genuinely exotic molecular pentaquark candidates comprising five different flavors, focusing on the $Ξ_b^{{(\prime,\,*)}} \bar D<sup>{(*)}$ and $Ξ_c^{{(\prime,\,*)}} B<sup>{(*)}$ systems. Employing the one-boson-exchange model with the $S$-$D$ wave mixing and coupled-channel dynamics, we identify the most promising molecular pentaquark candidates comprising five different flavors. These include the $Ξ_b \bar D$, $Ξ_b^{\prime} \bar D$, $Ξ_c B$, and $Ξ_c^{\prime} B$ states with $I(J<sup>P)=0(1/2<sup>-)$, the $Ξ_b \bar D<sup>{*}$, $Ξ_b^{\prime} \bar D<sup>{*}$, $Ξ_c B<sup>{*}$, and $Ξ_c^{\prime} B<sup>{*}$ states with $I(J<sup>P)=0(1/2<sup>-,\,3/2<sup>-)$, the $Ξ_b^{*} \bar D$ and $Ξ_c^{*} B$ states with $I(J<sup>P)=0(3/2<sup>-)$, as well as the $Ξ_b^{*} \bar D<sup>{*}$ and $Ξ_c^{*} B<sup>{*}$ states with $I(J<sup>P)=0(1/2<sup>-,\,3/2<sup>-,\,5/2<sup>-)$. Importantly, these loosely bound states exhibit pronounced spin splittings across different total angular momentum configurations after incorporating the spin-dependent interactions or the channel couplings. In addition, we identify several possible isovector molecular pentaquark candidates within the $Ξ_b^{{(\prime,\,*)}} \bar D<sup>{(*)}$ and $Ξ_c^{{(\prime,\,*)}} B<sup>{(*)}$ systems. Our predictions provide clear targets for experimental searches at facilities such as LHCb and Belle II, where the unique five-flavor quark configuration offers a distinctive experimental signature.