Weak decays of heavy hadrons into dynamically generated resonances

In this paper, we present a review of recent works on weak decay of heavy mesons and baryons with two mesons, or a meson and a baryon, interacting strongly in the final state. The aim is to learn about the interaction of hadrons and how some particular resonances are produced in the reactions. It is shown that these reactions have peculiar features and act as filters for some quantum numbers which allow to identify easily some resonances and learn about their nature. The combination of basic elements of the weak interaction with the framework of the chiral unitary approach allow for an interpretation of results of many reactions and add a novel information to different aspects of the hadron…

Study ofBB¯*andB*B¯*interactions inI=1and relationship to theZb(10610),Zb(10650)states

We use the local hidden gauge approach in order to study the $B{\overline{B}}^{*}$ and ${B}^{*}{\overline{B}}^{*}$ interactions for isospin $I=1$. We show that both interactions via one light meson exchange are not allowed by the Okubo-Zweig-Iizuka rule and, for that reason, we calculate the contributions due to the exchange of two pions, interacting and noninteracting among themselves, and also due to the heavy vector mesons. Then, to compare all these contributions, we use the potential related to the heavy vector exchange as an effective potential corrected by a factor which takes into account the contribution of the other light meson exchanges. In order to look for poles, this effective…

χc1 decays into a pseudoscalar meson and a vector-vector molecule

We evaluate ratios of the $\chi_{c1}$ decay rates to $\eta$ ($\eta', K^-$) and one of the $f_0(1370)$, $f_0(1710)$, $f_2(1270)$, $f_2'(1525)$, $K^{*}_2(1430)$ resonances, which in the local hidden gauge approach are dynamically generated from the vector-vector interaction. With the simple assumption that the $\chi_{c1}$ is a singlet of SU(3), and the input from the study of these resonances as vector-vector molecular states, we describe the experimental ratio $\mathcal{B}(\chi_{c1} \rightarrow \eta f_2(1270))/ \mathcal{B}(\chi_{c1} \rightarrow \eta' f_2'(1525))$ and make predictions for six more ratios that can be tested in future experiments.

Molecular Ω states

Motivated by the recent finding of five Ωc states by the LHCb collaboration, and the successful reproduction of three of them in a recent approach searching for molecular states of meson–baryon with the quantum numbers of Ωc, we extend these ideas and make predictions for the interaction of meson–baryon in the beauty sector, searching for poles in the scattering matrix that correspond to physical states. We find several Ωb states: two states with masses 6405 MeV and 6465 MeV for JP=12−; two more states with masses 6427 MeV and 6665 MeV for 32−; and three states between 6500 and 6820 MeV, degenerate with JP=12−,32−, stemming from the interaction of vector–baryon in the beauty sector.

Ωc states with an extension of the local hidden gauge approach

Prediction of a $Z_c(4000)$ $D^* \bar D^*$ state and relationship to the claimed $Z_c(4025)$

After discussing the OZI suppression of one light meson exchange in the interaction of $D^* \bar D^*$ with isospin I=1, we study the contribution of two pion exchange to the interaction and the exchange of a heavy vector $J/\psi$. We find this latter mechanism weak but enough to barely bind the system in J=2 with a mass around 4000 MeV, while the effect of the two pion exchange is a net attraction but weaker than that from $J/\psi$ exchange. We discuss this state and try to relate it to the $Z_c(4025)$ state, above the $D^* \bar D^*$ threshold, claimed in an experiment at BES from and enhancement of the $D^* \bar D^*$ distribution close to threshold. Together with the results from a recent …

$f_1(1285)$ decays into $a_0(980)\pi^0$, $f_0(980)\pi^0$ and isospin breaking

We evaluate the decay width for the processes $f_1(1285) \to \pi^0 a_0(980)$ and $f_1(1285) \to \pi^0 f_0(980)$ taking into account that all three resonances are dynamically generated from the meson-meson interaction, the $f_1(1285)$ from $K^* \bar K -c.c$ and the $a_0(980)$, $f_0(980)$ from $\pi \eta, K \bar K$ and $\pi \pi, K \bar K$ respectively. We use a triangular mechanism similar to that of the $\eta(1405) \to \pi \pi \eta$, which provides a decay width for $f_1(1285) \to \pi^0 a_0(980)$ with a branching fraction of the order of 30%, in agreement with experiment. At the same time we evaluate the decay width for the isospin forbidden $f_1(1285) \to \pi^0 f_0(980)$, which appears when …

Study of the DKK and DKK¯ systems

Using the fixed center approximation to Faddeev equations, we investigate the $DKK$ and $DK\overline{K}$ three-body systems, considering that the $DK$ dynamically generates, through its $I=0$ component, the ${D}_{s0}^{*}(2317)$ molecule. According to our findings, for the $DK\overline{K}$ interaction we find evidence of a state $I({J}^{P})=1/2({0}^{\ensuremath{-}})$ just above the ${D}_{s0}^{*}(2317)\overline{K}$ threshold and around the $D{f}_{0}(980)$ threshold, with mass of about 2833--2858 MeV, made mostly of $D{f}_{0}(980)$. On the other hand, no evidence related to a state from the $DKK$ interaction is found. The state found could be seen in the $\ensuremath{\pi}\ensuremath{\pi}D$ inv…

Prediction of anI=1DD¯*state and relationship to the claimedZc(3900),Zc(3885)

We study here the interaction of $D{\overline{D}}^{*}$ in the isospin $I=1$ channel in light of recent theoretical advances that allow us to combine elements of the local hidden gauge approach with heavy quark spin symmetry. We find that the exchange of light $q\overline{q}$ is Okubo-Zweig-Iizuka (OZI) suppressed and thus we concentrate on the exchange of heavy vectors and of two pion exchange. The latter is found to be small compared to the exchange of heavy vectors, which then determines the strength of the interaction. A barely $D{\overline{D}}^{*}$ bound state decaying into ${\ensuremath{\eta}}_{c}\ensuremath{\rho}$ and $\ensuremath{\pi}J/\ensuremath{\psi}$ is found. At the same time we…

f1(1285) decays into a0(980)π0, f0(980)π0 and isospin breaking

We evaluate the decay width for the processes f1(1285) → π0a0(980) and f1(1285) → π0f0(980) taking into account that all three resonances are dynamically generated from the meson-meson interaction, the f1(1285) from K*K¯+cc and the a0 (980), f0(980) from πη, KK¯ and ππ, KK¯ respectively. We use a triangular mechanism similar to that of the η(1405)→ππη, which provides a decay width for f1 (1285) → π0a0 (980) with a branching fraction of the order of 30%, in agreement with experiment. At the same time we evaluate the decay width for the isospin forbidden f1(1285) → π0 f0(980), which appears when we consider different masses for the charged and neutral kaons, and show that it is much more supp…

Molecular $\Omega_c$ states generated from coupled meson-baryon channels

We have investigated $\Omega_c$ states that are dynamically generated from the meson-baryon interaction. We use an extension of the local hidden gauge to obtain the interaction from the exchange of vector mesons. We show that the dominant terms come from the exchange of light vectors, where the heavy quarks are spectators. This has as a consequence that heavy quark symmetry is preserved for the dominant terms in the $(1/m_Q)$ counting, and also that the interaction in this case can be obtained from the $\textrm{SU(3)}$ chiral Lagrangians. We show that for a standard value for the cutoff regulating the loop, we obtain two states with $J^{P}={1/2}^{-}$ and two more with $J^{P}={3/2}^{-}$, thr…

Doubly charmed Ξcc molecular states from meson-baryon interaction

Stimulated by the new experimental LHCb findings associated with the ${\mathrm{\ensuremath{\Omega}}}_{c}$ states, some of which we have described in a previous work as being dynamically generated through meson-baryon interaction, we have extended this approach to make predictions for new ${\mathrm{\ensuremath{\Xi}}}_{cc}$ molecular states in the $C=2$, $S=0$, and $I=1/2$ sector. These states manifest themselves as poles in the solution of the Bethe-Salpeter equation in coupled channels. The kernels of this equation were obtained using general Lagrangians coming from the hidden local gauge symmetry or massive Yang-Mills theory, and the interactions are dominated by the exchange of light vect…

Ωb−→(Ξc+K−)π− decay and the Ωc states

We study the weak decay ${\mathrm{\ensuremath{\Omega}}}_{b}^{\ensuremath{-}}\ensuremath{\rightarrow}({\mathrm{\ensuremath{\Xi}}}_{c}^{+}{K}^{\ensuremath{-}}){\ensuremath{\pi}}^{\ensuremath{-}}$, in view of the narrow ${\mathrm{\ensuremath{\Omega}}}_{c}$ states recently measured by the LHCb Collaboration and later confirmed by the Belle Collaboration. The ${\mathrm{\ensuremath{\Omega}}}_{c}(3050)$ and ${\mathrm{\ensuremath{\Omega}}}_{c}(3090)$ are described as meson-baryon molecular states, using an extension of the local hidden gauge approach in coupled channels. We investigate the $\mathrm{\ensuremath{\Xi}}D$, ${\mathrm{\ensuremath{\Xi}}}_{c}\overline{K}$, and ${\mathrm{\ensuremath{\Xi}}}_…

Binding of the BDD¯ and BDD systems

We study theoretically the $BD\overline{D}$ and $BDD$ systems to see if they allow for possible bound or resonant states. The three-body interaction is evaluated implementing the fixed center approximation to the Faddeev equations which considers the interaction of a $D$ or $\overline{D}$ particle with the components of a $BD$ cluster, previously proved to form a bound state. We find an $I({J}^{P})=1/2({0}^{\ensuremath{-}})$ bound state for the $BD\overline{D}$ system at an energy around 8925--8985 MeV within uncertainties, which would correspond to a bottom hidden-charm meson. In contrast, for the $BDD$ system, which would be bottom double-charm and hence manifestly exotic, we have found h…