Abstract: The discovery of the D*(s0)(2317) and D-s1(2460) resonances in the charmed-strange meson spectra revealed that formerly successful constituent quark models lose predictability in the vicinity of two-meson thresholds. The emergence of non-negligible effects due to meson loops requires an explicit evaluation of the interplay between Q (q) over bar and (Q (q) over bar)(q (q) over bar) Fock components. In contrast to the c (s) over bar sector, there is no experimental evidence of J(P) = 0(+), 1(+) bottom-strange states yet. Motivated by recent lattice studies, in this work the heavy-quark partners of the D*(s0)(2317) and D-s1(2460) states are analyzed within a heavy meson chiral unitary scheme. As a novelty, the coupling between the constituent quark-model P-wave (B) over bar (s) scalar and axial mesons and the (B) over bar (()*()) K channels is incorporated employing an effective interaction, consistent with heavy-quark spin symmetry, constrained by the lattice energy levels.

Abstract: In this work, we study systems composed of a rho/omega and B* meson pair. We find three bound states in isospin, spin-parity channels (1/2, 0(+)), (1/2, 1(+)), and (1/2, 2(+)). The state with J = 2 can be a good candidate for the B-2*(5747). We also study the rho B system, and a bound state with mass 5728 MeV and width around 20 MeV is obtained, which can be identified with the B-1(5721) resonance. In the case of I = 3/2, one obtains repulsion and, thus, no exotic (molecular) mesons in this sector are generated in the approach.

Abstract: Starting from a molecular picture for the X(3872) resonance, this state and its J(PC) = 2(++) heavy-quark spin symmetry partner [X-2(4012)] are analyzed within a model which incorporates possible mixings with 2P charmonium (c (c) over bar) states. Since it is reasonable to expect the bare chi(c1)(2P) to be located above the D (D) over bar* threshold, but relatively close to it, the presence of the charmonium state provides an effective attraction that will contribute to binding the X(3872), but it will not appear in the 2(++) sector. Indeed in the latter sector, the chi(c2)(2P) should provide an effective small repulsion, because it is placed well below the D*(D) over bar* threshold. We show how the 1(++) and 2(++) bare charmonium poles are modified due to the D-(*)(D) over bar ((*)) loop effects, and the first one is moved to the complex plane. The meson loops produce, besides some shifts in the masses of the charmonia, a finite width for the 1(++) dressed charmonium state. On the other hand, X(3872) and X-2(4012) start developing some charmonium content, which is estimated by means of the compositeness Weinberg sum rule. It turns out that in the heavy-quark limit, there is only one coupling between the 2P charmonia and the D-(*)(D) over bar ((*)) pairs. We also show that, for reasonable values of this coupling, leading to X(3872) molecular probabilities of around 70-90%, the X2 resonance destabilizes and disappears from the spectrum, becoming either a virtual state or one being located deep into the complex plane, with decreasing influence in the D*(D) over bar* scattering line. Moreover, we also discuss how around 10-30% charmonium probability in the X(3872) might explain the ratio of radiative decays of this resonance into psi(2S) gamma and J/psi gamma Finally, we qualitatively discuss within this scheme, the hidden bottom flavor sector, paying a special attention to the implications for the X-b and Xb(2) states, heavy-quark spin-flavor partners of the X(3872).

Abstract: We consider the X(3872) resonance as a J(PC) = 1(++) D (D) over bar* hadronic molecule. According to heavy quark spin symmetry, there will exist a partner with quantum numbers 2(++), X-2, which would be a D*(D) over bar* loosely bound state. The X-2 is expected to decay dominantly into D (D) over bar, D (D) over bar* and (D) over barD* in d-wave. In this work, we calculate the decay widths of the X-2 resonance into the above channels, as well as those of its bottom partner, X-b2, the mass of which comes from assuming heavy flavor symmetry for the contact terms. We find partial widths of the X-2 and X-b2 of the order of a few MeV. Finally, we also study the radiative X-2 -> D (D) over bar*gamma. and X-b2 -> (B) over bar B*gamma decays. These decay modes are more sensitive to the long-distance structure of the resonances and to the D (D) over bar* or B (B) over bar* final state interaction.

Abstract: We propose that the X(3915) observed in the J/psi x channel is the same state as the chi(c2)(3930), and the X(3960), observed in the Ds+Ds- channel, is an S-wave Ds+Ds- hadronic molecule. In addition, the J(PC) = 0(++) component in the B+ -> D+D-K+ assigned to the X(3915) in the current Review of Particle Physics has the same origin as the X(3960), which has a mass around 3.94 GeV. To check the proposal, the available data in the D (D) over bar and Ds+Ds- channels from both B decays and gamma gamma fusion reaction are analyzed considering both the D (D) over bar -D-s(D) over bar (s)-D*(D) over bar*-D-s*(D) over bar (s)* coupled channels with 0(++) and a 2(++) state introduced additionally. It is found that all the data in different processes can be simultaneously well reproduced, and the coupled-channel dynamics produce four hidden-charm scalar molecular states with masses around 3.73, 3.94, 3.99 and 4.23 GeV, respectively. The results may deepen our understanding of the spectrum of charmonia as well as of the interactions between charmed hadrons.