Du, M. L., Albaladejo, M., Fernandez-Soler, P., Guo, F. K., Hanhart, C., Meissner, U. G., et al. (2018). Towards a new paradigm for heavy-light meson spectroscopy. Phys. Rev. D, 98(9), 094018–8pp.
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.
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Albaladejo, M., Fernandez-Soler, P., Guo, F. K., & Nieves, J. (2017). Two-pole structure of the D-0*(2400). Phys. Lett. B, 767, 465–469.
Abstract: The so far only known charmed non-strange scalar meson is dubbed as D-0(*)(2400) in the Review of Particle Physics. We show, within the framework of unitarized chiral perturbation theory, that there are in fact two (I = 1/2, J(P) = 0(+)) poles in the region of the D-0(*)( 2400) in the coupled-channel D pi, D eta and D-s (K) over bar scattering amplitudes. With all the parameters previously fixed, we predict the energy levels for the coupled-channel system in a finite volume, and find that they agree remarkably well with recent lattice QCD calculations. This successful description of the lattice data is regarded as a strong evidence for the two-pole structure of the D-0(*)( 2400). With the physical quark masses, the poles are located at (2105(-8)(+6) – i102(-12)(+10)) MeV and (2451(-26)(+36) – i134(-8)(+7)) MeV, with the largest couplings to the D pi and D-s (K) over bar channels, respectively. Since the higher pole is close to the D-s (K) over bar threshold, we expect it to show up as a threshold enhancement in the D-s (K) over bar invariant mass distribution. This could be checked by high-statistic data in future experiments. We also show that the lower pole belongs to the same SU(3) multiplet as the D-s0(*)(2317) state. Predictions for partners in the bottom sector are also given.
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Albaladejo, M., Daub, J. T., Hanhart, C., Kubis, B., & Moussallamd, B. (2017). How to employ (B)over-bar(d)(0) -> J/psi(pi eta, (K)over-barK) decays to extract information on pi eta scattering. J. High Energy Phys., 04(4), 010–28pp.
Abstract: We demonstrate that dispersion theory allows one to deduce crucial information on pi eta scattering from the final-state interactions of the light mesons visible in the spectral distributions of the decays (B) over bar (0)(d) -> J/psi(pi(0)eta, K+K-, K-0 (K) over bar (0)). Thus high-quality measurements of these differential observables are highly desired. The corresponding rates are predicted to be of the same order of magnitude as those for (B) over bar (0)(d) -> J/psi pi(+)pi(-) measured recently at LHCb, letting the corresponding measurement appear feasible.
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Albaladejo, M., Fernandez-Soler, P., Nieves, J., & Ortega, P. G. (2017). Lowest-lying even-parity (B)over-bar(s) mesons: heavy-quark spin-flavor symmetry, chiral dynamics, and constituent quark-model bare masses. Eur. Phys. J. C, 77(3), 170–9pp.
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.
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Albaladejo, M., & Moussallam, B. (2017). Extended chiral Khuri-Treiman formalism for eta -> 3 pi and the role of the a(0)(980), f(0)(980) resonances. Eur. Phys. J. C, 77(8), 508–23pp.
Abstract: Recent experiments on eta -> 3 pi decays have provided an extremely precise knowledge of the amplitudes across the Dalitz region which represent stringent constraints on theoretical descriptions. We reconsider an approach in which the low-energy chiral expansion is assumed to be optimally convergent in an unphysical region surrounding the Adler zero, and the amplitude in the physical region is uniquely deduced by an analyticity-based extrapolation using the Khuri-Treiman dispersive formalism. We present an extension of the usual formalism which implements the leading inelastic effects from the K (K) over bar channel in the final-state pi pi interaction as well as in the initial-state eta pi interaction. The constructed amplitude has an enlarged region of validity and accounts in a realistic way for the influence of the two light scalar resonances f(0)(980) and a(0)(980) in the dispersive integrals. It is shown that the effect of these resonances in the low-energy region of the eta -> 3 pi decay is not negligible, in particular for the 3 pi(0) mode, and improves the description of the energy variation across the Dalitz plot. Some remarks are made on the scale dependence and the value of the double quark mass ratio Q.
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Albaladejo, M., Guo, F. K., Hanhart, C., Meissner, U. G., Nieves, J., Nogga, A., et al. (2017). Note on X(3872) production at hadron colliders and its molecular structure. Chin. Phys. C, 41(12), 121001–3pp.
Abstract: The production of the X (3872) as a hadronic molecule in hadron colliders is clarified. We show that the conclusion of Bignamini et al., Phys. Rev. Lett. 103 (2009) 162001, that the production of the X(3872) at high pT implies a non-molecular structure, does not hold. In particular, using the well understood properties of the deuteron wave function as an example, we identify the relevant scales in the production process.
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Oset, E. et al, Albaladejo, M., Nieves, J., Fernandez-Soler, P., & Sun, Z. F. (2016). Weak decays of heavy hadrons into dynamically generated resonances. Int. J. Mod. Phys. E, 25(1), 1630001–105pp.
Abstract: 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 interaction and the properties of dynamically generated resonances.
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Albaladejo, M., Nieves, J., Oset, E., Sun, Z. F., & Liu, X. (2016). Can X(5568) be described as a B-s pi, B(K)over-bar resonant state? Phys. Lett. B, 757, 515–519.
Abstract: The DO Collaboration has recently seen a resonant-like peak in the B-s pi invariant mass spectrum, claimed to be a new state called X(5568). Using a B-s pi-B (K) over bar coupled channel analysis, implementing unitarity, and with the interaction derived from Heavy Meson Chiral Perturbation Theory, we are able to reproduce the reported spectrum, with a pole that can be associated to the claimed X(5568) state, and with mass and width in agreement with the ones reported in the experimental analysis. However, if the T-matrix regularization is performed by means of a momentum cutoff, the value for the latter needed to reproduce the spectrum is Lambda = 2.80 +/- 0.04 GeV, which is much larger than a “natural” value Lambda similar or equal to 1 GeV. In view of this, it is difficult to interpret the nature of this new state. This state would not qualify as a resonance dynamically generated by the unitarity loops. Assuming the observed peak to correspond to a physical state, we make predictions for partners in the D, D*, and B* sectors. Their observation (or lack thereof) would shed light into this issue.
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Albaladejo, M., Guo, F. K., Hidalgo-Duque, C., & Nieves, J. (2016). Z(c)(3900): What has been really seen? Phys. Lett. B, 755, 337–342.
Abstract: The Z(c)(+/-)(3900)/Z(c)(+/-)(3885) resonant structure has been experimentally observed in the Y(4260) -> J/Psi pi pi and Y(4260) -> (D) over bar* D pi decays. This structure is intriguing since it is a prominent candidate of an exotic hadron. Yet, its nature is unclear so far. In this work, we simultaneously describe the (D) over bar* D and J/Psi pi invariant mass distributions in which the Z(c) peak is seen using amplitudes with exact unitarity. Two different scenarios are statistically acceptable, where the origin of the Z(c) state is different. They correspond to using energy dependent or independent (D) over bar *D S-wave interaction. In the first one, the Z(c) peak is due to a resonance with a mass around the D (D) over bar* threshold. In the second one, the Z(c) peak is produced by a virtual state which must have a hadronic molecular nature. In both cases the two observations, Z(c)(+/-)(3900) and Z(c)(+/-)(3885), are shown to have the same common origin, and a (D) over bar *D bound state solution is not allowed. Precise measurements of the line shapes around the D (D) over bar* threshold are called for in order to understand the nature of this state.
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Albaladejo, M., Nieves, J., Oset, E., & Jido, D. (2016). Ds0*(2317) and DK scattering in B decays from BaBar and LHCb data. Eur. Phys. J. C, 76(6), 300–8pp.
Abstract: We study the experimental DK invariant mass spectra of the reactions B+ -> (D) over bar (DK+)-D-0-K-0, B-0 -> D-(DK+)-K-0 (measured by the BaBar collaboration) and B-s -> pi(+DK-)-K-0 measured by the LHCb collaboration), where an enhancement right above the threshold is seen. We show that this enhancement is due to the presence of D-s0*(2317), which is a D K bound state in the I (J(P)) = 0(0(+)) sector. We employ a unitarized amplitude with an interaction potential fixed by heavy meson chiral perturbation theory. We obtain a mass M-Ds0* = 2315(-17) (+12 +10)(-5) MeV, and we also show, by means of theWeinberg compositeness condition, that the DK component in the wave function of this state is P-DK = 70(-6 -8)(+4 +4) %, where the first (second) error is statistical (systematic).
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