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Xie, J. J., Chen, H. X., & Oset, E. (2011). The pp -> p Lambda K(+) and pp -> p Sigma(0)K(+) reactions with chiral dynamics. Phys. Rev. C, 84(3), 034004–8pp.
Abstract: We report on a theoretical study of the pp -> p Lambda K(+) and pp -> p Sigma(0)K(+) reactions near threshold using a chiral dynamical approach. The production process is described by single-pion and single-kaon exchange. The final state interactions of nucleon-hyperon, K-hyperon, and K-nucleon systems are also taken into account. We show that our model leads to a fair description of the experimental data on the total cross section of the pp -> p Lambda K(+) and pp -> p Sigma(0)K(+) reactions. We find that the experimental observed strong suppression of Sigma(0) production compared to Lambda production at the same excess energy can be explained. However, ignorance of phases between some amplitudes does not allow one to properly account for the nucleon-hyperon final state interaction for the pp -> p Sigma(0)K(+) reaction. We also demonstrate that the invariant mass distribution and the Dalitz plot provide direct information about the Lambda and Sigma(0) production mechanisms and may be tested by experiments at COSY or HIRFL-CSR.
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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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Liu, B. C., & Xie, J. J. (2012). The K- p -> eta Lambda reaction in an effective Lagrangian model. Phys. Rev. C, 85(3), 038201–4pp.
Abstract: We report on a theoretical study of the K- p -> eta Lambda reaction near threshold by using an effective Lagrangian approach. The role of s-channel Lambda(1670), t-channel K*, and u-channel proton pole diagrams are considered. We show that the total cross section data are well reproduced. However, only including the s-wave Lambda(1670) state and the background contribution from t and u channels is not enough to describe the bowl structures in the angular distribution of the K- p -> eta Lambda reaction, which indicates that there should be higher partial waves contributing to this reaction in some energy region. Indeed, if we considered the contributions from a D-03 resonance, we could describe the bowl structures; however, a rather small width (similar to 2 MeV) of this resonance would be needed.
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Xie, J. J., & Oset, E. (2012). The DN, pi Sigma(c) interaction in finite volume and the Lambda(c)(2595) resonance. Eur. Phys. J. A, 48(10), 146–10pp.
Abstract: In this work the interaction of the coupled channels DN and pi Sigma(c) in an SU(4) extrapolation of the chiral unitary theory, where the Lambda(c)(2595) resonance appears as dynamically generated from that interaction, is extended to produce results in finite volume. Energy levels in the finite box are evaluated and, assuming that they would correspond to lattice results, the inverse problem of determining the phase shifts in the infinite volume from the lattice results is solved. We observe that it is possible to obtain accurate pi Sigma(c) phase shifts and the position of the Lambda(c)(2595) resonance, but it requires the explicit consideration of the two coupled channels. We also observe that some of the energy levels in the box are attached to the closed DN channel, such that their use to induce the pi Sigma(c) phase shifts via Luscher's formula leads to incorrect results.
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Garzon, E. J., Xie, J. J., & Oset, E. (2013). Case in favor of the N*(1700)(3/2(-)). Phys. Rev. C, 87(5), 055204–12pp.
Abstract: Using an interaction extracted from the local hidden-gauge Lagrangians, which brings together vector and pseudoscalar mesons, and the coupled channels rho N (s wave), pi N (d wave), pi Delta (s wave), and pi Delta (d wave), we look in the region ofv root s = 1400-1850 MeV and find two resonances dynamically generated by the interaction of these channels, which are naturally associated to N*(1520)(3/2(-)) and N*(1700)(3/2(-)). N*(1700)(3/2(-)) appears neatly as a pole in the complex plane. The free parameters of the theory are chosen to fit the pi N (d-wave) data. Both the real and imaginary parts of the pi N amplitude vanish in our approach in the vicinity of this resonance, which is similar to what happens in experimental determinations and which makes this signal very weak in this channel. This feature could explain why this resonance does not show up in some experimental analyses, but the situation is analogous to that of the f(0)(980) resonance, the second scalar meson after sigma[f(0)(500)] in the pi pi(d-wave) amplitude. The unitary coupled channel approach followed here, in connectionwith the experimental data, leads automatically to a pole in the 1700-MeV region and makes this second 3/2-resonance unavoidable.
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