We perform a SU(3) analysis for both semi-leptonic and non-leptonic heavy meson weak decays into a pseudoscalar meson and a fully-light tetraquark in 10 or 27 representation. A reduction of the SU(3) representation tensor for the fully-light tetraqua
rks is produced and all the flavor components for each representation tensor are listed. The decay channels we analysis include $B/D to U/T~P~l u$, $B/D to U/T~P $ and $B_c to U/T~P/D$, with $U/T$ represents a fully-light tetraquark in 10 or 27 representation and $P$ is a pseudoscalar meson. Finally, among these results we list all the golden decay channels which are expected to have more possibilities to be observed in experiments.
In this work, the full leading order results of the form factors for $Xi_{b}toXi_{c}$ and $Lambda_{b}toLambda_{c}$ are obtained in QCD sum rules. Contributions from up to dim-5 have been considered. For completeness, we also study the two-point corre
lation function to obtain the pole residues of $Xi_{Q}$ and $Lambda_{Q}$, and higher accuracy is achieved. For the three-point correlation function, since stable Borel regions can not be found, about $20%$ uncertainties are introduced for the form factors of $Xi_{b}toXi_{c}$ and $Lambda_{b}toLambda_{c}$. Our results for the form factors are consistent with those of the Lattice QCD within errors.
We construct a leading-order effective field theory for both scalar and axial-vector heavy diquarks, and consider its power expansion in the heavy diquark limit. By assuming the transition from QCD to diquark effective theory, we derive the most gene
ral form for the effective diquark transition currents based on the heavy diquark symmetry. The short-distance coefficients between QCD and heavy diquark effective field theory are also obtained by a tree level matching. With the effective currents in the heavy diquark limit, we perform a reduction of the form factors for semi-leptonic decays of doubly heavy baryons, and find that only one nonperturbative function is remaining. It is shown that this soft function can be related to the Isgur-Wise function in heavy meson transitions. As a phenomenological application, we take a single pole structure for the reduced form factor, and use it to calculate the semi-leptonic decay widths of doubly heavy baryons. The obtained results are consistent with others given in the literature, and can be tested in the future.
We analyze the weak decay of doubly-heavy baryon decays into anti-triplets $Lambda_Q$ with light-cone sum rules. To calculate the decay form factors, both bottom and charmed anti-triplets $Lambda_b$ and $Lambda_c$ are described by the same set of lea
ding twist light-cone distribution functions. With the obtained form factors, we perform a phenomenology study on the corresponding semi-leptonic decays. The decay widths are calculated and the branching ratios given in this work are expected to be tested by future experimental data, which will help us to understand the underlying dynamics in doubly-heavy baryon decays.
