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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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Yao, D. L., Fernandez-Soler, P., Albaladejo, M., Guo, F. K., & Nieves, J. (2018). Heavy-to-light scalar form factors from Muskhelishvili-Omnes dispersion relations. Eur. Phys. J. C, 78(4), 310–26pp.
Abstract: By solving the Muskhelishvili-Omnes integral equations, the scalar form factors of the semileptonic heavy meson decays D -> pi(l) over bar nu(l), D -> (K) over bar(l) over bar nu(l), (K) over bar -> pi(l) over bar nu(l) and (B) over bar (s) -> Kl (nu) over bar (l) are simultaneously studied. As input, we employ unitarized heavy meson-Goldstone boson chiral coupled-channel amplitudes for the energy regions not far from thresholds, while, at high energies, adequate asymptotic conditions are imposed. The scalar form factors are expressed in terms of Omn\`es matrices multiplied by vector polynomials, which contain some undetermined dispersive subtraction constants. We make use of heavy quark and chiral symmetries to constrain these constants, which are fitted to lattice QCD results both in the charm and the bottom sectors, and in this latter sector to the light-cone sum rule predictions close to q(2)=0 as well. We find a good simultaneous description of the scalar form factors for the four semileptonic decay reactions. From this combined fit, and taking advantage that scalar and vector form factors are equal at q(2)=0, we obtain |V-cd| = 0.244 +/- 0.022, |V-cs| = 0.945 +/- 0.041 and |V-ub| = (4.3 +/- 0.7)x10(-3) for the involved Cabibbo-Kobayashi-Maskawa (CKM) matrix elements. In addition, we predict the following vector form factors at q(2) = 0: |f(+)(D ->eta)(0)| = 0.01 +/- 0.05, |f(+)(Ds ->eta)(0)| = 0.50 +/- 0.08, |f(+)(Ds ->eta)(0)| = 0.73 +/- 0.03 and|f(+)((B) over bar ->eta)(0)| = 0.82 +/- 0.08, which might serve as alternatives to determine the CKM elements when experimental measurements of the corresponding differential decay rates become available. Finally, we predict the different form factors above the q(2)-regions accessible in the semileptonic decays, up to moderate energies amenable to be described using the unitarized coupled-channel chiral approach.
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Albaladejo, M., Fernandez-Soler, P., Nieves, J., & Ortega, P. G. (2018). Contribution of constituent quark model c(s)over-bar states to the dynamics of the D*s0 (2317) and Ds1(2460) resonances. Eur. Phys. J. C, 78(9), 722–22pp.
Abstract: The masses of the D*(s0) (2317) and D-s1(2460) resonances lie below the DK and D* K thresholds respectively, which contradicts the predictions of naive quark models and points out to non-negligible effects of the D(*) K loops in the dynamics of the even-parity scalar (J(pi) = 0(+)) and axial-vector (J(pi) = 1(+)) c (s) over bar systems. Recent lattice QCD studies, incorporating the effects of the D(*) K channels, analyzed these spin-parity sectors and correctly described the D*(s0)(2317) – D-s1(2460) mass splitting. Motivated by such works, we study the structure of the D*(s0)(2317) and D-s1(2460) resonances in the framework of an effective field theory consistent with heavy quark spin symmetry, and that incorporates the interplay between D(*) K meson-meson degrees of freedom and bare P-wave c (s) over bar states predicted by constituent quark models. We extend the scheme to finite volumes and fit the strength of the coupling between both types of degrees of freedom to the available lattice levels, which we successfully describe. We finally estimate the size of the D(*) K two-meson components in the D*(s0)(2317) and D-s1(2460) resonances, and we conclude that these states have a predominantly hadronic-molecular structure, and that it should not be tried to accommodate these mesons within c (s) over bar constituent quark model patterns.
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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., Nieves, J., & Tolos, L. (2021). D(D)over-bar* scattering and chi(c1) (3872) in nuclear matter. Phys. Rev. C, 104(3), 035203–20pp.
Abstract: We study the behavior of the chi(c1) (3872), also known as X(3872), in dense nuclear matter. We begin from a picture in vacuum of the X(3872) as a purely molecular (D (D) over bar*-c.c.) state, generated as a bound state from a heavy-quark symmetry leading-order interaction between the charmed mesons, and analyze the D (D) over bar* scattering T matrix (T-D (D) over bar*) inside of the medium. Next, we consider also mixed-molecular scenarios and, in all cases, we determine the corresponding X(3872) spectral function and the D (D) over bar* amplitude, with the mesons embedded in the dense environment. We find important nuclear corrections for T-D (D) over bar* and the pole position of the resonance, and discuss the dependence of these results on the D (D) over bar* molecular component in the X(3872) wave function. These predictions could be tested in the finite-density regime that can be accessed in the future CBM and PANDA experiments at the Facility for Antiproton and Ion Research (FAIR).
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Rodas, A., Pilloni, A., Albaladejo, M., Fernandez-Ramirez, C., Mathieu, V., & Szczepaniak, A. P. (2022). Scalar and tensor resonances in J/psi radiative decays. Eur. Phys. J. C, 82(1), 80–17pp.
Abstract: We perform a systematic analysis of the J/psi -> gamma pi(0)pi(0) and -> gamma(KSKS0)-K-0 partial waves measured by BESIII. We use a large set of amplitude parametrizations to reduce the model bias. We determine the physical properties of seven scalar and tensor resonances in the 1-2.5 GeV mass range. These include the well known f(0)(1500) and f(0)(1710), that are considered to be the primary glueball candidates. The hierarchy of resonance couplings determined from this analysis favors the latter as the one with the largest glueball component.
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Du, M. L., Albaladejo, M., Guo, F. K., & Nieves, J. (2022). Combined analysis of the Z(c)(3900) and the Z(cs)(3985) exotic states. Phys. Rev. D, 105(7), 074018–20pp.
Abstract: We have performed a combined analysis of the BESIII data for both the Z(c)(3900) and Z(cs)(3985) structures, assuming that the latter is an SU(3) flavor partner of the former one. We have improved on the previous analysis of Albaladejo et al. [Phys. Lett. B 755, 337 (2016)] by computing the amplitude for the D-1(D) over barD* triangle diagram considering both D- and S-wave D1D*x couplings. We have also investigated effects from SU(3) light-flavor violations, which are found to be moderate and of the order of 20%. The successful reproduction of the BESIII spectra, in both the hidden-charm and hidden-charm strange sectors, strongly supports that the Z(cs)(3985) and Z(c)(3900) are SU(3) flavor partners placed in the same octet multiplet. The best results are obtained when an energy-dependent term in the diagonal D(*) (D) over bar ((s))((*)) interaction is included, leading to resonances (poles above the thresholds) to describe these exotic states. We have also made predictions for the isovector Z*c and isodoublet Z*(cs), D*(D) over bar*, and D*??D*s molecules, with J(PC) = 1(+-) and J(P) = 1(+), respectively. These states would be heavy-quark spin symmetry (HQSS) partners of the Z(c) and Z(cs). Besides the determination of the masses and widths of the Z(c)(3900) and Z(cs)(3985), we also predict those of the Z*(c) and Z*(cs) resonances.
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Albaladejo, M. (2022). T-cc(+) coupled channel analysis and predictions. Phys. Lett. B, 829, 137052–13pp.
Abstract: A coupled channel analysis of the D*D-+(0) and D*D-0(+) system is performed to study the doubly charmed T-cc(+) state recently discovered by the LHCb collaboration. We use a simple model for the scattering amplitude and production mechanism that allows us to describe well the experimental spectrum, and obtain the T-cc(+) pole in the coupled channel T-matrix. We find that this bound state has a large molecular component. The isospin (I = 0 or I = 1) of the state cannot be inferred from the (DD0)-D-0 pi(+) spectrum alone, although there is some experimental evidence that points to the I = 0 interpretation. Therefore, we use the same formalism to predict other DD pi spectra. In the case the T-cc(+) has I = 1, we also predict the location of the other two members (T-cc(+) and T-cc(0)) of the triplet. Finally, using Heavy-Quark Spin Symmetry, we predict the location of possible heavier D*D* (I = 0 or I= 1) partners.
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Albaladejo, M., & Nieves, J. (2022). Compositeness of S-wave weakly-bound states from next-to-leading order Weinberg's relations. Eur. Phys. J. C, 82(8), 724–12pp.
Abstract: We discuss a model-independent estimator of the likelihood of the compositeness of a shallow S-wave bound or virtual state. The approach is based on an extension of Weinberg's relations in Weinberg (Phys Rev 137:B672, 1965) and it relies only on the proximity of the energy of the state to the two-hadron threshold to which it significantly couples. The scheme only makes use of the experimental scattering length and the effective range low energy parameters, and it is shown to be fully consistent for predominantly molecular hadrons. As explicit applications, we analyse the case of the deuteron, the S-1(0) nucleon virtual state and the exotic D-so(*)(2317)(+/-) , and find strong support to the molecular interpretation in all cases. Results are less conclusive for the D* (s0)(2317)+/-, since the binding energy of this state would be significantly higher than that of the deuteron, and the approach employed here is at the limit of its applicability. We also qualitatively address the case of the recently discovered T + cc state, within the isospin limit to avoid the complexity of the very close thresholds (DD)-D-0*+ and D + D*(0), which could mask the ingredients of the approach proposed in this work.
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Albaladejo, M., Bibrzycki, L., Dawid, S. M., Fernandez-Ramirez, C., Gonzalez-Solis, S., Hiller Blin, A. N., et al. (2022). Novel approaches in hadron spectroscopy. Prog. Part. Nucl. Phys., 127, 103981–75pp.
Abstract: The last two decades have witnessed the discovery of a myriad of new and unexpected hadrons. The future holds more surprises for us, thanks to new-generation experiments. Understanding the signals and determining the properties of the states requires a parallel theoretical effort. To make full use of available and forthcoming data, a careful amplitude modeling is required, together with a sound treatment of the statistical uncertainties, and a systematic survey of the model dependencies. We review the contributions made by the Joint Physics Analysis Center to the field of hadron spectroscopy.
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