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Richard, J. M., Valcarce, A., & Vijande, J. (2020). Hall-Post inequalities: Review and application to molecules and tetraquarks. Ann. Phys., 412, 168009–32pp.
Abstract: A review is presented of the Hall-Post inequalities that give lower-bounds to the ground-state energy of quantum systems in terms of energies of smaller systems. New applications are given for systems experiencing both a static source and inner interactions, as well as for hydrogen-like molecules and for tetraquarks in some quark models. In the latter case, the Hall-Post inequalities constrain the possibility of deeply-bound exotic mesons below the threshold for dissociation into two quark-antiquark mesons. We also emphasize the usefulness of the Hall-Post bounds in terms of 3-body energies when some 2-body subsystems are ill defined or do not support any bound state.
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Garcilazo, H., Valcarce, A., & Vijande, J. (2017). (4)(Lambda Lambda) n system. Chin. Phys. C, 41(7), 074102–6pp.
Abstract: Using local central Yukawa-type Malfliet-Tjon interactions reproducing the low-energy parameters and phase shifts of the nn system, and the latest updates of the n Lambda and Lambda Lambda Nijmegen ESCO8c potentials, we study the possible existence of a (4)(Lambda Lambda)n bound state. Our results indicate that the (4)(Lambda Lambda)n is unbound, being just above threshold. We discuss the role played by the S-1(0) nn repulsive term of the Yukawa-type Malfliet-Tjon interaction.
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Garcilazo, H., Valcarce, A., & Vijande, J. (2020). Xi(-)t quasibound state instead of Lambda Lambda nn bound state. Chin. Phys. C, 44(2), 024102–7pp.
Abstract: The coupled Lambda Lambda nn – Xi-pnn system was studied to investigate whether the inclusion of channel coupling is able to bind the Lambda Lambda nn system. We use a separable potential three-body model of the coupled Lambda Lambda nn – Xi-pnn system and a variational four-body calculation with realistic interactions. Our results exclude the possibility of a bound state by a large margin. Instead, we found a Xi(-)t quasibound state above the Lambda Lambda nn threshold.
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Vijande, J., Valcarce, A., Carames, T. F., & Richard, J. M. (2014). Multiquark Systems. Few-Body Syst., 55(8-10), 675–681.
Abstract: In this talk we tackle the description of hadron spectroscopy in terms of the constituent quark model. We focus on the mesonic charm sector, where several of the new reported resonances seem to defy their classification as simple quark-antiquark states. We pay special attention to higher order Fock space components in describing excited states of the meson spectra in close connection with the hadron-hadron interaction. The main goal of the present study is a coherent understanding of the low-energy hadron phenomenology without enforcing any particular model, to constrain its characteristics and learn about low-energy realization of the theory.
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Valcarce, A., Vijande, J., Richard, J. M., & Garcilazo, H. (2018). Stability of Heavy Tetraquarks. Few-Body Syst., 59(2), 9–7pp.
Abstract: We discuss the stability of tetraquark systems with two different masses. After some reminders about the stability of very asymmetric QQ (q) over bar(q) over bar tetraquarks, we demonstrate that in the all-heavy limit q -> Q, the system becomes unstable for standard color-additive models. We also analyze the consequences of symmetry breaking for Qq (Q) over bar(q) over bar configurations: we find a kind of metastability between the lowest threshold Q (Q) over bar + q (q) over bar and the highest one, Q (q) over bar + (Q) over barq, and we calculate the width of the resonance. Our results are consistent with the experimental observation of narrow hadrons lying well above their lowest decay threshold.
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Vijande, J., Valcarce, A., Carames, T. F., & Garcilazo, H. (2013). Heavy Hadron Spectroscopy: A Quark Model Perspective. Int. J. Mod. Phys. E, 22(5), 1330011–25pp.
Abstract: We present recent results of hadron spectroscopy and hadron hadron interaction from the perspective of constituent quark models. We pay special attention to the role played by higher-order hock space components in the hadron spectra and the connection of this extension with the hadron-hadron interaction. The main goal of our description is to obtain a coherent understanding of the low-energy hadron phenomenology without enforcing any particular model, to constrain its characteristics and learn about the low-energy realization of the theory.
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Garcilazo, H., Valcarce, A., & Vijande, J. (2020). Neutral baryonic systems with strangeness. Int. J. Mod. Phys. E, 29(1), 1930009–22pp.
Abstract: We review the status as regards to the existence of three- and four-body bound states made of neutrons and Lambda hyperons. For interesting cases, the coupling to neutral baryonic systems made of charged particles of different strangeness has been addressed. There are strong arguments showing that the Lambda nn system has no bound states. Lambda Lambda nn strong stable states are not favored by our current knowledge of the strangeness -1 and -2 baryon-baryon interactions. However, a possible Xi(-) t quasibound state decaying to Lambda Lambda nn might exist in nature. Similarly, there is a broad agreement about the nonexistence of Lambda Lambda n bound states. However, the coupling to Xi NN states opens the door to a resonance above the Lambda Lambda n threshold.
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Vijande, J., Valcarce, A., Carames, T. F., & Garcilazo, H. (2013). Heavy hadron spectroscopy: A quark model perspective. Nucl. Phys. A, 914, 472–481.
Abstract: We present recent results of hadron spectroscopy and hadron-hadron interaction from the perspective of constituent quark models. We pay special attention to the role played by higher order Fock space components in the hadron spectra and the connection of this extension with the hadron-hadron interaction. The main goal of our description is to obtain a coherent understanding of the low-energy hadron phenomenology without enforcing any particular model, to constrain its characteristics and learn about low-energy realization of the theory.
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Garcilazo, H., Valcarce, A., & Vijande, J. (2016). Maximal isospin few-body systems of nucleons and Xi hyperons. Phys. Rev. C, 94(2), 024002–3pp.
Abstract: By using local central Yukawa-type interactions that reproduce the low-energy parameters of the latest updates of the Nijmegen ESC08c potentials, we show that the N Xi, NN Xi, N Xi Xi, and NN Xi Xi systems with maximal isospin are bound. Since in these states the strong decay N Xi -> Lambda Lambda is forbidden by isospin conservation, these strange few-body systems will be stable under the strong interaction. These results may suggest that other states with different number of Ns and Xi s in the maximal isospin channel could also be bound.
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Richard, J. M., Valcarce, A., & Vijande, J. (2018). Few-body quark dynamics for doubly heavy baryons and tetraquarks. Phys. Rev. C, 97(3), 035211–10pp.
Abstract: We discuss the adequate treatment of the three- and four-body dynamics for the quark model picture of double-charm baryons and tetraquarks. We stress that the variational and Born-Oppenheimer approximations give energies very close to the exact ones, while the diquark approximation might be somewhat misleading. The Hall-Post inequalities also provide very useful lower bounds that exclude the possibility of stable tetraquarks for some mass ratios and some color wave functions.
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