Strong decays of $${\bar{D}}^{*}K^{*}$$ molecules and the newly observed $$X_{0,1}$$ states

Lately, the LHCb Collaboration reported the discovery of two new states in the $$B^+\rightarrow D^+D^- K^+$$ B + → D + D - K + decay, i.e., $$X_0(2866)$$ X 0 ( 2866 ) and $$X_1(2904)$$ X 1 ( 2904 ) . In the present work, we study whether these states can be understood as $${\bar{D}}^*K^*$$ D ¯ ∗ K ∗ molecules from the perspective of their two-body strong decays into $$D^-K^+$$ D - K + via triangle diagrams and three-body decays into $${\bar{D}}^*K\pi $$ D ¯ ∗ K π . The coupling of the two states to $${\bar{D}}^*K^*$$ D ¯ ∗ K ∗ are determined from the Weinberg compositeness condition, while the other relevant couplings are well known. The obtained strong decay width for the $$X_0(2866)$$ X 0 ( 2866 ) state, in marginal agreement with the experimental value within the uncertainty of the model, hints at a large $${\bar{D}}^*K^*$$ D ¯ ∗ K ∗ component in its wave function. On the other hand, the strong decay width for the $$X_1(2904)$$ X 1 ( 2904 ) state, much smaller than its experimental counterpart, effectively rules out its assignment as a $${\bar{D}}^*K^*$$ D ¯ ∗ K ∗ molecule.

Novel Ideas in Nonleptonic Decays of Double Heavy Baryons

The recent discovery of double charm baryon states by the LHCb Collaborarion and their high precision mass determination calls for a comprehensive analysis of the nonleptonic decays of double and single heavy baryons. Nonleptonic baryon decays play an important role in particle phenomenology since they allow for studying the interplay of long and short distance dynamics of the Standard Model (SM). Furthermore, they allow one to search for New Physics effects beyond the SM. We review recent progress in experimental and theoretical studies of the nonleptonic decays of heavy baryons with a focus on double charm baryon states and their decays. In particular, we discuss new ideas proposed by the present authors to calculate the W-exchange matrix elements of the nonleptonic decays of double heavy baryons. An important ingredient in our approach is the compositeness condition of Salam and Weinberg, and an effective implementation of infrared confinement both of which allow one to describe the nonperturbative structure of baryons composed of light and heavy quarks. Furthermore, we discuss an ab initio calculational method for the treatment of the so-called W-exchange diagrams generated by W ± boson exchange between quarks. We found that the W ± -exchange contributions are not suppressed in comparison with the tree-level (factorizing) diagrams and must be taken into account in the evaluation of matrix elements. Moreover, there are decay processes such as the doubly Cabibbo-suppressed decay Ξ c + → p ϕ recently observed by the LHCb Collaboration, which is contributed to only by one single W-exchange diagram.

MESON BARYON COMPONENTS IN THE STATES OF THE BARYON DECUPLET

We extend the Weinberg compositeness condition to partial waves of L = 1 and resonant states to determine the weight of meson-baryon component in the [Formula: see text] baryon decuplet. We obtain an appreciable weight of πN in the Δ(1232) wave function, of the order of 60 % and we also show that, as we go to higher energies in the members of the decuplet, the weights of meson-baryon component decrease and they already show a dominant part for a genuine component in the wave function. We interpret the meaning of the Weinberg sum-rule extended to complex energies.