Aceti, F., Oset, E., & Roca, L. (2014). Composite nature of the Lambda (1520) resonance. Phys. Rev. C, 90(2), 025208–8pp.
Abstract: Recently, the Weinberg compositeness condition of a bound state was generalized to account for resonant states and higher partial waves. We apply this extension to the case of the Lambda (1520) resonance and quantify the weight of the meson-baryon components in contrast to other possible genuine building blocks. This resonance was theoretically obtained from a coupled channels analysis using the s-wave pi Sigma* and K Xi* and the d-wave (K) over bar N and pi Sigma channels, applying the techniques of the chiral unitary approach. We obtain the result that this resonance is essentially dynamically generated from these meson-baryon channels, leaving room for only 15% weight of other kinds of components in its wave function.
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Garzon, E. J., & Oset, E. (2015). Mixing of pseudoscalar-baryon and vector-baryon in the J(P)=1/2(-) sector and the N* (1535) and N* (1650) resonances. Phys. Rev. C, 91(2), 025201–7pp.
Abstract: We study the meson-baryon interaction with J(P) = 1/2 using the hidden-gauge Lagrangians and mixing pseudoscalar meson-baryon with the vector meson-baryon states in a coupled channels scheme with pi N, eta N, K Lambda, K Sigma, rho N, and pi Delta (d wave). We fit the subtraction constants of each channel to the S-11 partial wave amplitude of the pi N scattering data extracted from the partial wave analysis of the George Washington group. We find two poles that we associate to the N*(1535) and the N*(1650) resonances, with negative subtraction constants of natural size, and compare the results with empirical determinations of these pole positions. We calculate the branching ratios for the different channels of each resonance and we find a good agreement with the experimental data. The cross section for the pi(-)p -> eta n scattering is also evaluated and compared with experiment.
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Ren, X. L., Oset, E., Alvarez-Ruso, L., & Vicente Vacas, M. J. (2015). Antineutrino induced Lambda(1405) production off the proton. Phys. Rev. C, 91(4), 045201–11pp.
Abstract: We have studied the strangeness-changing antineutrino-induced reactions (v) over bar (l)p -> l(+)phi B, with phi B = K(-)p, (K) over bar (0)n, pi(0)Lambda, pi(0)Sigma(0), eta Lambda, eta Sigma(0), pi(+)Sigma(-), pi(-)Sigma(+), K+Xi(-), and K-0 Xi(0), using a chiral unitary approach. These ten coupled channels are allowed to interact strongly, using a kernel derived from the chiral Lagrangians. This interaction generates two Lambda(1405) poles, leading to a clear single peak in the pi Sigma invariant mass distributions. At backward scattering angles in the center-of-mass frame, (nu) over bar (mu)p -> mu(+)pi(0)Sigma(0) is dominated by the Lambda(1405) state at around 1420 MeV while the lighter state becomes relevant as the angle decreases, leading to an asymmetric line shape. In addition, there are substantial differences in the shape of pi Sigma invariant mass distributions for the three charge channels. If observed, these differences would provide valuable information on a claimed isospin I = 1, strangeness S = -1 baryonic state around 1400 MeV. Integrated cross sections have been obtained for the pi Sigma and (K) over barN channels and the impact of unitarization in the results has been investigated. The number of events with Lambda(1405) excitation in (nu) over bar μp collisions in the recent antineutrino run at the Main Injector Experiment for nu-A (MINER nu A) has also been obtained. We find that this reaction channel is relevant enough to be investigated experimentally and to be taken into account in the simulation models of future experiments with antineutrino beams.
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Miyahara, K., Hyodo, T., & Oset, E. (2015). Weak decay of Lambda(+)(c) for the study of Lambda(1405) and Lambda(1670). Phys. Rev. C, 92(5), 055204–8pp.
Abstract: We study the Lambda(c) decay process to pi(+) and the meson-baryon final state for the analysis of Lambda resonances. Considering the Cabibbo-Kobayashi-Maskawamatrix, color suppression, diquark correlation, and the kinematical condition, we show that the final meson-baryon state should be in a pure I = 0 combination, when the meson-baryon invariantmass is small. Because the I = 1 contamination usually makes it difficult to analyze Lambda resonances directly from experiments, the Lambda(c) decay is an ideal process to study Lambda resonances. Calculating the final-state interaction by chiral unitary approaches, we find that the pi Sigma invariant mass distributions have the same peak structure in the all charge combination of the pi Sigma states related to the higher pole of the two poles of the Lambda(1405). Furthermore, we obtain a clear Lambda(1670) peak structure in the (K) over bar N and eta Lambda spectra.
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Xie, J. J., Oset, E., & Geng, L. S. (2016). Photoproduction of the f(2)'(1525), a(2)(1320), and K-2(*) (1430). Phys. Rev. C, 93(2), 025202–8pp.
Abstract: Assuming that the f(2)'(1525), a(2)(1320), and K-2(*) (1430) resonances are dynamically generated states from vector-meson-vector-meson interactions in the s-wave with spin S = 2, we study the gamma p -> f(2)'(1525)p, gamma p -> a(2)(0)(1320)p, and gamma p -> K-2(*)(1430)Lambda(Sigma) reactions. These reactions proceed in the following way: the incoming photon first mutates into a rho(0), omega, or phi meson via vector-meson dominance, which then interacts with the rho(0), omega, or K* emitted by the incoming proton to form the tensor mesons f(2)(')(1525), a(2)(1320), and K-2(*)(1430). The picture is simple and has no free parameters, as all the parameters of the mechanism have been fixed in previous studies. We predict the differential and total cross sections of these reactions. The results can be tested in future experiments and therefore offer new clues about the nature of these tensor states.
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