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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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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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Pavon Valderrama, M., Xie, J. J., & Nieves, J. (2012). Are there three Xi (1950) states? Phys. Rev. D, 85(1), 017502–5pp.
Abstract: Different experiments on hadron spectroscopy have long suspected the existence of several cascade states in the 1900-2000 MeV region. They are usually labeled under the common name of Xi (1950). As we argue here, there are also theoretical reasons supporting the idea of several Xi (1950) resonances. In particular, we propose the existence of three Xi (1950) states: one of these states would be part of a spinparity 1/2(-) decuplet and the other two probably would belong to the 5/2(+) and 5/2(-) octets. We also identify which decay channels are more appropriate for the detection of each of the previous states.
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Nieves, J., Ruiz Simo, I., & Vicente Vacas, M. J. (2012). The nucleon axial mass and the MiniBooNE quasielastic neutrino-nucleus scattering problem. Phys. Lett. B, 707(1), 72–75.
Abstract: The charged-current double differential neutrino cross section, measured by the MiniBooNE Collaboration, has been analyzed using a microscopical model that accounts for, among other nuclear effects, long range nuclear (RPA) correlations and multinucleon scattering. We find that MiniBooNE data are fully compatible with the world average of the nucleon axial mass in contrast with several previous analyses which have suggested an anomalously large value. We also discuss the reliability of the algorithm used to estimate the neutrino energy.
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Garcia-Recio, C., Nieves, J., Salcedo, L. L., & Tolos, L. (2012). D- mesic atoms. Phys. Rev. C, 85(2), 025203–13pp.
Abstract: The anti-D meson self-energy is evaluated self-consistently, using unitarized coupled-channel theory, by computing the in-medium meson-baryon T matrix in the C = -1, S = 0 sector. The heavy pseudo-scalar and heavy vector mesons, (D) over bar and (D) over bar*, are treated on equal footing as required by heavy-quark spin symmetry. Results for energy levels and widths of (D) over bar (-) mesic atoms in C-12, Ca-40, Sn-118, and Pb-208 are presented. The spectrum contains states of atomic and of nuclear types for all nuclei. (D) over bar (0)-nucleus bound states are also obtained. We find that, after electromagnetic and nuclear cascade, these systems end up with the (D) over bar bound in the nucleus, either as a meson or as part of an exotic (D) over barN (pentaquark) loosely bound state.
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