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Xie, J. J., & Nieves, J. (2010). Role of the N * (2080) resonance in the (gamma)over-right-arrowp -> K+ Lambda(1520) reaction. Phys. Rev. C, 82(4), 045205–8pp.
Abstract: We investigate the Lambda (1520) photoproduction in the (gamma) over right arrowp -> K+ Lambda(1520) reaction within the effective Lagrangian method near threshold. In addition to the “background” contributions from the contact, t-channel K-exchange, and s-channel nucleon pole terms, which were already considered in previous studies, the contribution from the nucleon resonance N*(2080) (spin-parity J(P) = 3/2(-)) is also considered. We show that the inclusion of the nucleon resonance N*(2080) leads to a fairly good description of the new LEPS differential cross-section data, and that these measurements can be used to determine some of the properties of this latter resonance. However, serious discrepancies appear when the predictions of the model are compared to the photon-beam asymmetry, which was also measured by the LEPS Collaboration.
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Xie, J. J., Martinez Torres, A., Oset, E., & Gonzalez, P. (2011). Plausible explanation for the Delta(5/2)+(2000) puzzle. Phys. Rev. C, 83(5), 055204–11pp.
Abstract: From a Faddeev calculation for the pi-(Delta rho)(N5/2)-(1675) system we show the plausible existence of three dynamically generated I (J(P)) = 3/2(5/2(+)) baryon states below 2.3 GeV, whereas only two resonances, Delta(5/2)+ (1905)( ) and Delta(5/2)+(2000)(**), are cataloged in the Particle Data Book Review. Our results give theoretical support to data analyses extracting two distinctive resonances, Lambda(5/2)+(similar to 1740) and Lambda(5/2)+(similar to 2200), from which the mass of Delta(5/2)+ (2000) is estimated. We propose that these two resonances should be cataloged instead of Delta(5/2)+(2000). This proposal gets further support from the possible assignment of the other baryon states found in the approach in the I = 1/2, 3/2 with J(P) = 1/2(+), 3/2(+), 5/(2)+ sectors to known baryonic resonances. In particular, Delta(1/2)+(1750)(*) is naturally interpreted as a pi N-1/2-(1650) bound state.
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Xie, J. J., Martinez Torres, A., & Oset, E. (2011). Faddeev fixed-center approximation to the N K K(bar) system and the signature of a N*(1920)(1/2+) state. Phys. Rev. C, 83(6), 065207–8pp.
Abstract: We perform a calculation for the three-body N (K) over barK scattering amplitude by using the fixed-center approximation to the Faddeev equations, taking the interaction between N and (K) over bar, N and K, and (K) over bar and K from the chiral unitary approach. The resonant structures show up in the modulus squared of the three-body scattering amplitude and suggest that a N (K) over barK hadron state can be formed. Our results are in agreement with others obtained in previous theoretical works, which claim a new N* resonance around 1920 MeV with spin-parity J(P) = 1/2(+). The existence of these previous works allows us to test the accuracy of the fixed center approximation in the present problem and sets the grounds for possible application in similar problems, as an explorative tool to determine bound or quasibound three-hadron systems.
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Xie, J. J., Liang, W. H., Oset, E., Moskal, P., Skurzok, M., & Wilkin, C. (2017). Determination of the eta He-3 threshold structure from the low energy pd -> eta He-3 reaction. Phys. Rev. C, 95(1), 015202–9pp.
Abstract: We analyze the data on cross sections and asymmetries for the pd -> eta He-3 reaction close to threshold and look for bound states of the eta He-3 system. Rather than parameterizing the scattering matrix, as is usually done, we develop a framework in which the eta He-3 optical potential is the key ingredient, and its strength, together with some production parameters, are fitted to the available experimental data. The relationship of the scattering matrix to the optical potential is established using the Bethe-Salpeter equation and the eta He-3 loop function incorporates the range of the interaction given by the empirical He-3 density. We find a local Breit-Wigner form of the eta He-3 amplitude T below threshold with a clear peak in vertical bar T vertical bar(2), which corresponds to an eta He-3 binding of about 0.3 MeV and a width of about 3 MeV. By fitting the potential we can also evaluate the eta He-3 scattering length, including its sign, thus resolving the ambiguity in the former analyses.
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Xie, J. J., Liang, W. H., & Oset, E. (2016). (K)over-bar-induced formation of the f(0)(980) and a(0)(980) resonances on proton targets. Phys. Rev. C, 93(3), 035206–8pp.
Abstract: We perform a calculation of the cross section for nine reactions induced by (K) over bar scattering on protons. The reactions studied are K- p -> Lambda pi(+)pi(-), K- p -> Sigma(0)pi(+)pi(-), K- p -> Lambda pi(0)eta, K- p -> Sigma(0)pi(0)eta, K- p -> Sigma(+)pi(-)eta, (K) over bar (0) p -> Lambda pi(+)eta, (K) over bar (0) p -> Sigma(0)pi(+)eta, (K) over bar (0) p -> Sigma(+)pi(+)pi(-), and (K) over bar (0) p -> Sigma+pi(0)eta. We find that in the reactions producing pi(+)pi(-), a clear peak for the f(0)(980) resonance is found, while no trace of f(0)(500) appears. Similarly, in the cases of p. production, a strong peak is found for the a(0)(980) resonance, with the characteristic strong cusp shape. Cross sections and invariant mass distributions are evaluated which should serve, by comparing them with future data, to test the dynamics of the chiral unitary approach used for the evaluations and the nature of these resonances.
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