Molecular interpretation of the LHCb pentaquarks from an analysis of J/ψp spectrum

A coupled-channel approach including the ΛcD¯(*) and ηcp channels in addition to the Σc(*)D¯(*) and J/ψp channels, as required by unitarity and heavy quark spin symmetry (HQSS), is applied to the hidden-charm pentaquark Pc states, i.e., Pc(4312), Pc(4440) and Pc(4457), discovered by LHCb Collaboration. It is demonstrated that to obtain cutoff independent results, the one-pion exchange potential in the multichannel systems is to be supplemented with next-leading order counter terms responsible for the S-wave-to-D-wave transitions. We show that the experimental data for the J/ψp mass distributions are fully in line with the ΣcD¯ and ΣcD¯* hadronic molecular interpretation of the Pc(4312) and Pc(4440)/Pc(4457), respectively. A narrow Σc*D¯ molecule around 4.38 GeV is required by the HQSS with the evidence for its existence seen in the J/ψp spectrum. Moreover, we predict the line shapes for the elastic and inelastic channels.

Masses and strong decays of open charm hexaquark states $$\Sigma _{c}^{(*)}{\Sigma }_{c}^{(*)}$$

Inspired by the recent discovery of the doubly charmed tetraquark state $$T_{cc}^{+}$$ T cc + by the LHCb Collaboration, we perform a systematic study of masses and strong decays of open charm hexaquark states $${\Sigma }_{c}^{(*)}\Sigma _{c}^{(*)}$$ Σ c ( ∗ ) Σ c ( ∗ ) . Taking into account heavy quark spin symmetry breaking, we predict several bound states of isospin $$I=0$$ I = 0 , $$I=1$$ I = 1 , and $$I=2$$ I = 2 in the one boson exchange model. Moreover, we adopt the effective Lagrangian approach to estimate the decay widths of $${\Sigma }_{c}^{(*)}\Sigma _{c}^{(*)} \rightarrow \Lambda _{c}\Lambda _{c}$$ Σ c ( ∗ ) Σ c ( ∗ ) → Λ c Λ c and their relevant ratios via the triangle diagram mechanism, which range from a few MeV to a few tens of MeV. We strongly recommend future experimental searches for the $${\Sigma }_{c}^{(*)}\Sigma _{c}^{(*)}$$ Σ c ( ∗ ) Σ c ( ∗ ) hexaquark states in the $$\Lambda _c\Lambda _c$$ Λ c Λ c invariant mass distributions.

Symmetries, Partners and Thresholds: The Case of the Xb

The discovery of the X(3872) meant the revival of the heavy meson spectroscopy beyond naive qq¯ structures. Since the SU(3) scheme, which was very useful in the dawn of the quark models, does not work for these states, one has to use new symmetries, like Heavy Quark Spin Symmetry (HQSS) and Heavy Flavor Symmetry (HFS), to look for new states. However, at the energy regions where these new states appear, new factors are involved and it is not straightforward to relate the predictions of the symmetries with the data. In this work, we present a critical analysis of this problem and show, in a coupled-channels model, how the relative position of the bare QQ¯ states with respect to meson-meson thresholds and the coupling with other channels modulate the strength of the interaction and, hence, modify the structure of the predicted states. We found a possible candidate to the X(3872) partner at 10,599 MeV/c2.