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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Debastiani, V. R., Sakai, S., & Oset, E. (2017). Role of a triangle singularity in the pi N(1535) contribution to gamma p -> p pi(0) eta. Phys. Rev. C, 96(2), 025201–7pp.
Abstract: We have studied the gamma p -> p pi(0) eta reaction paying attention to the two main mechanisms at low energies, the gamma p ->Delta(1700) -> eta Delta(1232) and the gamma p -> Delta(1700) -> pi N(1535). Both are driven by the photoexcitation of the Delta (1700) and the second one involves a mechanism that leads to a triangle singularity. We are able to evaluate quantitatively the cross section for this process and show that it agrees with the experimental determination. Yet there are some differences with the standard partial wave analysis which does not include explicitly the triangle singularity. The exercise also shows the convenience of exploring possible triangle singularities in other reactions and how a standard partial wave analysis can be extended to accommodate them.
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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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Martinez Torres, A., Khemchandani, K. P., & Oset, E. (2023). Theoretical study of the gamma d -> pi(0)eta d reaction. Phys. Rev. C, 107(2), 025202–24pp.
Abstract: We have done a theoretical study of the gamma d -> pi(0)eta d reaction starting with a realistic model for the gamma N -> pi(0)eta N reaction that reproduces cross sections and polarization observables at low energies and involves the gamma N -> Delta(1700) -> eta Delta(1232) -> eta pi N-0 process. For the coherent reaction in the deuteron we considered the impulse approximation together with the rescattering of the pions and the eta on a different nucleon than the one where they are produced. We found this second mechanism very important since it helps share between two nucleons the otherwise large momentum transfer of the reaction. Other contributions to the gamma d -> pi(0)eta d reaction, involving the gamma N -> pi(+/-)pi N-0' process, followed by the rescattering of the pi(+/-) with another nucleon to give eta and a nucleon, have also been included. We find a natural explanation, tied to the dynamics of our model, for the shift of the eta-d mass distribution to lower invariant masses, and of the pi(0)-d mass distribution to larger invariant masses, compared to a phase space calculation. We also study theoretical uncertainties related to the large momenta of the deuteron wave function involved in the process as well as to the couplings present in the model. Striking differences are found with the experimental angular distribution and further theoretical investigations might be necessary.
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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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Alvarez-Ruso, L., Graczyk, K. M., & Saul-Sala, E. (2019). Nucleon axial form factor from a Bayesian neural-network analysis of neutrino-scattering data. Phys. Rev. C, 99(2), 025204–14pp.
Abstract: The Bayesian approach for feedforward neural networks has been applied to the extraction of the nucleon axial form factor from the neutrino-deuteron-scattering data measured by the Argonne National Laboratory bubble-chamber experiment. This framework allows to perform a model-independent determination of the axial form factor from data. When the low 0.05 < Q(2) < 0.10-GeV2 data are included in the analysis, the resulting axial radius disagrees with available determinations. Furthermore, a large sensitivity to the corrections from the deuteron structure is obtained. In turn, when the low-Q(2) region is not taken into account with or without deuteron corrections, no significant deviations from previous determinations have been observed. A more accurate determination of the nucleon axial form factor requires new precise measurements of neutrino-induced quasielastic scattering on hydrogen and deuterium.
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Xie, J. J., Wang, E., & Zou, B. S. (2014). Role of the Delta*(1940) in the pi(+) p -> K+ Sigma(+)(1385) and pp -> nK(+) Sigma(+)(1385) reactions. Phys. Rev. C, 90(2), 025207–11pp.
Abstract: The pp -> nK(+)Sigma(+)(1385) reaction is a very good isospin 3/2 filter for studying Delta(++)* resonance decaying to K+Sigma(+)(1385). Within the effective Lagrangian method, we investigate the Sigma (1385) (spin parity J(P) = 3/2(+)) hadronic production in the pi(+) p -> K+Sigma(+)(1385) and pp -> nK(+)Sigma(+)(1385) reactions. For the pi(+) p -> K+Sigma(+)(1385) reaction, in addition to the “background” contributions from t-channel K*(0) exchange and u-channel Lambda(1115) and Sigma(0)(1193) exchange, we also consider the contribution from the s-channel Delta*(1940) resonance, which has significant coupling to the K Sigma(1385) channel. We show that the inclusion of the Delta*(1940) resonance leads to a fairly good description of the low-energy experimental total cross section data of pi(+)p -> K+Sigma(+)(1385) reaction. Basing on the study of the pi(+)p -> K+Sigma(+)(1385) reaction and with the assumption that the excitation of Delta*(1940) resonance dominates the pp -> nK(+)Sigma(+)(1385) reaction, we calculate the total and differential cross sections of the pp -> nK(+)Sigma(+)(1385) reaction. It is shown that the new experimental data support the important role played by the Delta*(1940) resonance with a mass in the region of 1940 MeV and a width of around 200 MeV. We also demonstrate that the invariant mass distribution and the Dalitz plot provide direct information of the Sigma(+)(1385) production, which can be tested by future experiments.
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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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Xie, J. J., & Wilkin, C. (2010). Associated strangeness production in the pp -> pK(+) K(-)p and pp -> pK(+)pi(0)Sigma(0) reactions. Phys. Rev. C, 82(2), 025210–6pp.
Abstract: The total and differential cross sections for associated strangeness production in the pp -> pK(+) K(-)p and pp -> pK(+)pi(0)Sigma(0) reactions have been studied in a unified approach using an effective Lagrangian model. It is assumed that both the K(-)p and pi(0)Sigma(0) final states originate from the decay of the Lambda(1405) that was formed in the production chain pp -> p(N*(1535). K+ Lambda(1405)). The available experimental data are well reproduced, especially the ratio of the two total cross sections, which is much less sensitive to the particular model of the entrance channel. The significant coupling of the N*(1535) to Lambda(1405)K is further evidence for large ss components in the quark wave function of the N*(1535).
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Pastore, A., Martini, M., Davesne, D., Navarro, J., Goriely, S., & Chamel, N. (2014). Linear response theory and neutrino mean free path using Brussels-Montreal Skyrme functionals. Phys. Rev. C, 90(2), 025804–11pp.
Abstract: The Brussels-Montreal Skyrme functionals have been successful in describing properties of both finite nuclei and infinite homogeneous nuclear matter. In their latest version, these functionals have been equipped with two extra density-dependent terms in order to reproduce simultaneously ground state properties of nuclei and infinite nuclear matter properties while avoiding at the same time the arising of ferromagnetic instabilities. In the present article, we extend our previous results of the linear response theory to include such extra terms at both zero and finite temperature in pure neutron matter. The resulting formalism is then applied to derive the neutrino mean free path. The predictions from the Brussels-Montreal Skyrme functionals are compared with ab initio methods.
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