Abstract: Since 2003 many new hadrons, including the lowest-lying positive-parity charm-strange mesons D*(s0) (2317) and D-s1 (2460), have been observed that do not conform with quark-model expectations. It was recently demonstrated that various puzzles in the charm-meson spectrum find a natural resolution if the SU(3) multiplets for the lightest scalar and axial-vector states, among them the D*(s0) (2317) and the D-s1 (2460), owe their existence to the nonperturbative dynamics of Goldstone-boson scattering off D-(s) and D*((s)) mesons. Most importantly the ordering of the lightest strange and nonstrange scalars becomes natural. We demonstrate for the first time that this mechanism is strongly supported by the recent high quality data on the B- -> D+ pi(-)pi(-) provided by the LHCb experiment. This implies that the lowest quark-model positive-parity charm mesons, together with their bottom counterparts, if realized in nature, do not form the ground-state multiplet. This is similar to the pattern that has been established for the scalar mesons made from light up, down, and strange quarks, where the lowest multiplet is considered to be made of states not described by the quark model. In a broader view, the hadron spectrum must be viewed as more than a collection of quark-model states.

Abstract: We have analyzed the singularities of a triangle loop integral in detail and derived a formula for an easy evaluation of the triangle singularity on the physical boundary. It is applied to the Lambda(b) -> J/psi K(-)p process via Lambda*-charmonium-proton intermediate states. Although the evaluation of absolute rates is not possible, we identify the chi(c1) and the psi(2S)as the relatively most relevant states among all possible charmonia up to the psi(2S). The Lambda(1890)chi(c1)p loop is very special, as its normal threshold and triangle singularities merge at about 4.45 GeV, generating a narrow and prominent peak in the amplitude in the case that the chi(c1)p is in an S wave. We also see that loops with the same charmonium and other Lambda* hyperons produce less dramatic peaks from the threshold singularity alone. For the case of chi(c1)p -> J/psi p and quantum numbers 3/2(-) or 5/2(+), one needs P and D waves, respectively, in the chi(c1)p, which drastically reduce the strength of the contribution and smooth the threshold peak. In this case, we conclude that the singularities cannot account for the observed narrow peak. In the case of 1/2(+), 3/2(-) quantum numbers, where chi(c1)p -> J/psi p can proceed in an S wave, the Lambda(1890)chi(c1)p triangle diagram could play an important role, though neither can assert their strength without further input from experiments and lattice QCD calculations.

Abstract: We explore the consequences of heavy flavor, heavy quark spin, and heavy antiquark-diquark symmetries for hadronic molecules within an effective field theory framework. Owing to heavy antiquark-diquark symmetry, the doubly heavy baryons have approximately the same light-quark structure as the heavy antimesons. As a consequence, the existence of a heavy meson-antimeson molecule implies the possibility of a partner composed of a heavy meson and a doubly heavy baryon. In this regard, the D (D) over bar* molecular nature of the X(3872) will hint at the existence of several baryonic partners with isospin I = 0 and J(P) = 5(-)/2 or 3(-)/2. Moreover, if the Z(b)(10650) turns out to be a B*(B) over bar* bound state, we can be confident of the existence of Xi(bb)*(B) over bar* hadronic molecules with quantum numbers I(J(P)) = 1(1(-)/2) and I(J(P)) = 1(3/2(-)). These states are of special interest since they can be considered to be triply heavy pentaquarks.