Bottom baryon decays to pseudoscalar meson and pentaquark

Based on SU(3) flavor symmetry, we decompose the decay amplitudes of bottom baryon decays to a pseudoscalar meson and an octet (a decuplet) pentaquark in terms of three (two) invariant amplitudes $T_1$ and $T_{2,3}$ (${\tilde{T}}_1$ and ${\tilde{T}}_2$) corresponding to external $W$-emission and internal $W$-emission diagrams, respectively. For antitriplet bottom baryons ${\mathrm{\Lambda }}_b^0$, ${\mathrm{\Xi }}_b^0$, and ${\mathrm{\Xi }}_b^{-}$, their decays to a decuplet pentaquark proceed only through the internal $W$-emission diagram. Assuming the dominance from the external $W$-emission amplitudes, we present an estimate of the decay rates relative to ${\mathrm{\Lambda }}_b^0\to P_p^{+}{K}^{-}$, where $P_p^{+}$ is the hidden-charm pentaquark with the same light-quark content as the proton. Hence, our numerical results will provide a very useful guideline to the experimental search for pentaquarks in bottom baryon decays. For example, ${\mathrm{\Xi }}_b^0\to P_{{\mathrm{\Sigma }}^{+}}{K}^{-}$, ${\mathrm{\Xi }}_b^{-}\to P_{{\mathrm{\Sigma }}^{-}}{\overline{K}}^0$, ${\mathrm{\Omega }}_b^{-}\to P_{{\mathrm{\Xi }}^{-}}{\overline{K}}^0$, and ${\mathrm{\Omega }}_b^{-}\to P_{{\mathrm{\Xi }}^0}{K}^{-}$ may have rates comparable to that of ${\mathrm{\Lambda }}_b^0\to P_p^{+}{K}^{-}$ and these modes should be given the higher priority in the experimental searches for pentaquarks.

Figure 1

External $W$-emission (a) and internal $W$-emission diagrams (b) and (c) for the bottom baryon decays to a pseudoscalar meson and a pentaquark. Note that the amplitude of (c) is the same as that of (b) up to a sign, since the former corresponds to switching $k$ and $l$ in the initial diquark state of the latter, which is antisymmetric (symmetric) under the interchange of two light quarks of the antitriplet (sextet) bottom baryon.