Yamagata-Sekihara, J., Nieves, J., & Oset, E. (2011). Couplings in coupled channels versus wave functions in the case of resonances: Application to the two A(1405) states. Phys. Rev. D, 83(1), 014003–15pp.
Abstract: In this paper we develop a formalism to evaluate wave functions in momentum and coordinate space for the resonant states dynamically generated in a unitary coupled channel approach. The on-shell approach for the scattering matrix, commonly used, is also obtained in quantum mechanics with a separable potential, which allows one to write wave functions in a trivial way. We develop useful relationships among the couplings of the dynamically generated resonances to the different channels and the wave functions at the origin. The formalism provides an intuitive picture of the resonances in the coupled channel approach, as bound states of one bound channel, which decays into open ones. It also provides an insight and practical rules for evaluating couplings of the resonances to external sources and how to deal with final state interaction in production processes. As an application of the formalism we evaluate the wave functions of the two A(1405) states in the pi Sigma, (K) over barN, and other coupled channels. It also offers a practical way to study three-body systems when two of them cluster into a resonance.
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Garcia-Recio, C., Geng, L. S., Nieves, J., & Salcedo, L. L. (2011). Low-lying even-parity meson resonances and spin-flavor symmetry. Phys. Rev. D, 83(1), 016007–30pp.
Abstract: Based on a spin-flavor extension of chiral symmetry, a novel s-wave meson-meson interaction involving members of the rho nonet and of the pi octet is introduced, and its predictions are analyzed. The starting point is the SU(6) version of the SU(3)-flavor Weinberg-Tomozawa Lagrangian. SU(6) symmetry-breaking terms are then included to account for the physical meson masses and decay constants in a way that preserves (broken) chiral symmetry. Next, the T-matrix amplitudes are obtained by solving the Bethe-Salpeter equation in a coupled-channel scheme, and the poles are identified with their possible Particle Data Group counterparts. It is shown that most of the low-lying even-parity Particle Data Group meson resonances, especially in the J(P) = 0(+) and 1(+) sectors, can be classified according to multiplets of SU(6). The f(0)(1500), f(1)(1420), and some 0(+)(2(++)) resonances cannot be accommodated within this scheme, and thus they would be clear candidates to be glueballs or hybrids. Finally, we predict the existence of five exotic resonances (I >= 3/2 and/or vertical bar Y vertical bar = 2) with masses in the range of 1.4-1.6 GeV, which would complete the 27(1), 10(3), and 10(3)* multiplets of SU(3) circle times SU(2).
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Nieves, J., Ruiz Simo, I., & Vicente Vacas, M. J. (2011). Inclusive charged-current neutrino-nucleus reactions. Phys. Rev. C, 83(4), 045501–19pp.
Abstract: We present a model for weak charged-current induced nuclear reactions at energies of interest for current and future neutrino oscillation experiments. This model is a natural extension of the work in Refs. [1,2], where the quasielastic contribution to the inclusive electron and neutrino scattering on nuclei was analyzed. The model is based on a systematic many-body expansion of the gauge boson absorption modes that includes one, two, and even three-body mechanisms, as well as the excitation of Delta isobars. The whole scheme has no free parameters, besides those previously adjusted to the weak pion production off the nucleon cross sections in the deuteron, since all nuclear effects were set up in previous studies of photon, electron, and pion interactions with nuclei. We have discussed at length the recent charged-current quasielastic MiniBooNE cross section data, and showed that two-nucleon knockout mechanisms are essential to describing these measurements.
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Du, M. L., Filin, A., Baru, V., Dong, X. K., Epelbaum, E., Guo, F. K., et al. (2023). Role of Left-Hand Cut Contributions on Pole Extractions from Lattice Data: Case Study for Tcc(3875)+. Phys. Rev. Lett., 131(13), 131903–7pp.
Abstract: We discuss recent lattice data for the T_{cc}(3875)^{+} state to stress, for the first time, a potentially strong impact of left-hand cuts from the one-pion exchange on the pole extraction for near-threshold exotic states. In particular, if the left-hand cut is located close to the two-particle threshold, which happens naturally in the DD^{*} system for the pion mass exceeding its physical value, the effective-range expansion is valid only in a very limited energy range up to the cut and as such is of little use to reliably extract the poles. Then, an accurate extraction of the pole locations requires the one-pion exchange to be implemented explicitly into the scattering amplitudes. Our findings are general and potentially relevant for a wide class of hadronic near-threshold states.
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Gamermann, D., Garcia-Recio, C., Nieves, J., & Salcedo, L. L. (2011). Odd-parity light baryon resonances. Phys. Rev. D, 84(5), 056017–30pp.
Abstract: We use a consistent SU(6) extension of the meson-baryon chiral Lagrangian within a coupled channel unitary approach in order to calculate the T matrix for meson-baryon scattering in the s wave. The building blocks of the scheme are the pi and N octets, the rho nonet and the UDELTA; decuplet. We identify poles in this unitary T matrix and interpret them as resonances. We study here the nonexotic sectors with strangeness S = 0, -1, -2, -3 and spin J = 1/2, 3/2 and 5/2. Many of the poles generated can be asociated with known N, UDELTA;, sigma, Lambda, Xi and Omega resonances with negative parity. We show that most of the low-lying three and four star odd-parity baryon resonances with spin 1/2 and 3/2 can be related to multiplets of the spin-flavor symmetry group SU(6). This study allows us to predict the spin-parity of the Xi (1620), Xi (1690), Xi (1950), Xi (2250), Omega (2250) and Omega (2380) resonances, which have not been determined experimentally yet.
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Nieves, J., & Valderrama, M. P. (2011). Deriving the existence of B(B)over-bar* bound states from the X(3872) and heavy quark symmetry. Phys. Rev. D, 84(5), 056015–21pp.
Abstract: We discuss the possibility and the description of bound states between B and (B) over bar* mesons. We argue that the existence of such a bound state can be deduced from (i) the weakly bound X(3872) state, (ii) certain assumptions about the short-range dynamics of the D (D) over bar* system and (iii) heavy quark symmetry. From these assumptions the binding energy of the possible B (B) over bar* bound states is determined, first in a theory containing only contact interactions which serves as a straightforward illustration of the method, and then the effects of including the one-pion exchange potential are discussed. In this latter case three isoscalar states are predicted: a positive and negative C-parity (3)S(1) – (3)D(1) state with a binding energy of 20 MeV and 6 MeV below threshold, respectively, and a positive C-parity (3)P(0) shallow state located almost at the B (B) over bar* threshold. However, large uncertainties are generated as a consequence of the 1/m(Q) corrections from heavy quark symmetry. Finally, the newly discovered isovector Z(b)(10610) state can be easily accommodated within the present framework by a minor modification of the short-range dynamics.
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Hernandez, E., & Nieves, J. (2011). Study of the strong Sigma(b) -> Lambda(b)pi and Sigma*(b) -> Lambda(b)pi in a nonrelativistic quark model. Phys. Rev. D, 84(5), 057902–5pp.
Abstract: We present results for the strong widths corresponding to the Sigma(b) -> Lambda(b)pi and Sigma*(b) -> Lambda(b)pi decays. We apply our model from Phys. Rev. D 72, 094022 (2005), where we previously studied the corresponding transitions in the charmed sector. Our nonrelativistic constituent quark model uses wave functions that take advantage of the constraints imposed by heavy quark symmetry. The partial conservation of axial current hypothesis allows us to determine the strong vertices from an analysis of the axial current matrix elements.
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Albertus, C., Hernandez, E., & Nieves, J. (2011). Exclusive c -> s, d semileptonic decays of ground-state spin-1/2 doubly charmed baryons. Phys. Lett. B, 704(5), 499–509.
Abstract: We evaluate exclusive semileptonic decays of ground-state spin-1/2 doubly heavy charmed baryons driven by a c -> s, d transition at the quark level. Our results for the form factors are consistent with heavy quark spin symmetry constraints which are valid in the limit of an infinitely massive charm quark and near zero recoil. Only a few exclusive semileptonic decay channels have been theoretically analyzed before. For those cases we find that our results are in a reasonable agreement with previous calculations.
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Nieves, J., Pich, A., & Ruiz Arriola, E. (2011). Large-N(C) properties of the rho and f(0)(600) mesons from unitary resonance chiral dynamics. Phys. Rev. D, 84(9), 096002–20pp.
Abstract: We construct pi pi amplitudes that fulfill exact elastic unitarity, account for one-loop chiral perturbation theory contributions and include all 1/N(C) leading terms, with the only limitation of considering just the lowest-lying nonet of exchanged resonances. Within such a scheme, the N(C) dependence of sigma and rho masses and widths is discussed. Robust conclusions are drawn in the case of the rho resonance, confirming that it is a stable meson in the limit of a large number of QCD colors, N(C). Less definitive conclusions are reached in the scalar-isoscalar sector. With the present quality of data, we cannot firmly conclude whether or not the N(C) = 3 f(0)(600) resonance completely disappears at large N(C) or if it has a subdominant component in its structure, which would become dominant for a number of quark colors sufficiently large.
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Flynn, J. M., Hernandez, E., & Nieves, J. (2012). Triply heavy baryons and heavy quark spin symmetry. Phys. Rev. D, 85(1), 014012–10pp.
Abstract: We study the semileptonic b -> c decays of the lowest-lying triply heavy baryons made from b and c quarks in the limit m(b), m(c) >> Lambda(QCD) and close to the zero-recoil point. The separate heavy-quark spin symmetries strongly constrain the matrix elements, leading to single form factors for ccb -> ccc, bbc -> ccb, and bbb -> bbc baryon decays. We also study the effects on these systems of using a Y-shaped confinement potential, as suggested by lattice QCD results for the interaction between three static quarks.
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