We look into the newly observed (2012) state from the molecular perspective in which the resonance is generated from theK * , η andK channels. We find that this picture provides a natural explanation of the properties of the (2012) state. We stress that the molecular nature of the resonance is revealed with a large coupling of the (2012) to theK * channel, that can be observed in the (2012) → K π decay which is incorporated automatically in our chiral unitary approach via the use of the spectral function of * in the evaluation of theK * loop function.

We have reviewed the renormalization procedure used in the unitarized coupled-channel model of Romanets et al. (Phys Rev D 85:114032, 2012), and its impact in the , , and sector, where five states have been recently observed by the LHCb Collaboration. The meson-baryon interactions used in the model are consistent with both chiral and heavy-quark spin symmetries, and lead to a successful description of the observed lowest-lying odd parity resonances and , and and resonances. We show that some (probably at least three) of the states observed by LHCb will also have odd parity and or , belonging two of them to the same  HQSS multiplets as the latter charmed and beauty baryons.

In this work we study several c and b states dynamically generated from the meson-baryon interaction in coupled channels, using an extension of the local hidden gauge approach in the Bethe-Salpeter equation. These molecular states appear as poles of the scattering amplitudes, and several of them can be identified with the experimentally observed c states, including the c (2790), c (2930), c (2970), c (3055) and c (3080). Also, for the recently reported b (6227) state, we find two poles with masses and widths remarkably close to the experimental data, for both the J P = 1/2 − and J P = 3/2 − sectors.

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The decay of Λ þ c into π þ π 0 Λð1405Þ with the Λð1405Þ decay into π 0 Σ 0 through a triangle diagram is studied. This process is initiated by Λ þ c → π þKÃ N, and then theK Ã decays intoKπ andKN produce the Λð1405Þ through a triangle loop containingK Ã NK which develops a singularity around 1890 MeV. This process is prohibited by the isospin symmetry, but the decay into this channel is enhanced by the contribution of the triangle diagram, which is sensitive to the mass of the internal particles. We find a narrow peak in the π 0 Σ 0 invariant mass distribution, which originates from the Λð1405Þ amplitude, but is tied to the mass differences between the charged and neutralK or N states. The observation of the unavoidable peak of the triangle singularity in the isospin-violating Λð1405Þ production would provide further support for the hadronic molecular picture of the Λð1405Þ and further information on theKN interaction.

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We study odd parity J = 1/2 and J = 3/2 c resonances using a unitarized coupled-channel framework based on a SU(6) lsf ×HQSS-extended Weinberg-Tomozawa baryon-meson interaction, while paying a special attention to the renormalization procedure. We predict a large molecular cK component for the c (2790) with a dominant 0 − light-degree-of-freedom spin configuration. We discuss the differences between the 3/2 − c (2625) and c (2815) states, and conclude that they cannot be SU(3) siblings, whereas we predict the existence of other c-states, one of them related to the two-pole structure of the c (2595). It is of particular interest a pair of J = 1/2 and J = 3/2 poles, which form a HQSS doublet and that we tentatively assign to the c (2930) and c (2970), respectively. Within this picture, the c (2930) would be part of a SU(3) sextet, containing either the c (3090) or the c (3119), and that would be completed by the c (2800). Moreover, we identify a J = 1/2 sextet with the b (6227) state and the recently discovered b (6097). Assuming the equal spacing rule and to complete this multiplet, we predict the existence of a J = 1/2 b odd parity state, with a mass of 6360 MeV and that should be seen in the bK channel.

We study the implications for b → * c ν and b → * c π − [ * c = c (2595) and c (2625)] decays that can be deduced from heavy quark spin symmetry (HQSS). Identifying the odd parity c (2595) and c (2625) resonances as HQSS partners, with total angular momentumparity j P q = 1 − for the light degrees of freedom, we find that the ratios (b → c (2595)π −)/ (b → c (2625)π −) and (b → c (2595) ν)/ (b → c (2625) ν) agree, within errors, with the experimental values given in the Review of Particle Physics. We discuss how future, and more precise, measurements of the above branching fractions could be used to shed light into the inner HQSS structure of the narrow c (2595) odd-parity resonance. Namely, we show that such studies would constrain the existence of a sizable j P q = 0 − component in its wave-function, and/or of a two-pole pattern, in analogy to the case of the similar (1405) resonance in the strange sector, as suggested by most of the approaches that describe the c (2595) as a hadron molecule. We also investigate the lepton flavor universality ratios R[ * c ] = B(b → * c τν τ)/B(b → * c μν μ), and discuss how R[ c (2595)] may be affected by a new source of potentially large systematic errors if there are two c (2595) poles. CQM c (2595) and CQM c (2625) resonances would correspond to the members of the HQSS-doublet associated to (λ = 1, ρ = 0), with total spin S q = 0 for the light degrees of freedom (ldof), leading to a spin-flavor-spatial symmetric wave-function for the light isoscalar diquark subsystem inside of the * c baryon. The total spins of these states are the result of coupling the orbital-angular momentum λ of the brown muck-with respect to the heavy quark-with the spin (S Q) of the latter. Thus both CQM c (2595) and CQM c (2625) states are con-(*)++ c + π −)