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Doring, M., Oset, E., & Meissner, U. G. (2010). Evaluation of the polarization observables I-S and I-C in the reaction gamma p -> pi(0)eta p. Eur. Phys. J. A, 46(2), 315–323.
Abstract: We evaluate the polarization observables I-S and I-C for the reaction gamma p -> pi(0)eta p, using a chiral unitary framework developed earlier. The I-S and I-C observables have been recently measured for the first time by the CBELSA/TAPS Collaboration. The theoretical predictions of I-S and I-C, given for altogether 18 angle-dependent functions, are in good agreement with the measurements. Also, the asymmetry d Sigma/dcos theta evaluated here agrees with the data. We show the importance of the Delta(1700) D-33-resonance and its S-wave decay into eta Delta(1232). The result can be considered as a further confirmation of the dynamical nature of this resonance. At the highest energies, deviations of the predictions from the data start to become noticeable, which leaves room for additional processes and resonances such as a Delta(1940) D-33. We also point out how to further improve the calculation.
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Guo, F. K., Meissner, U. G., Nieves, J., & Yang, Z. (2016). Remarks on the P-c structures and triangle singularities. Eur. Phys. J. A, 52(10), 318–6pp.
Abstract: It was proposed that the narrow P-c(4450) structure observed by the LHCb Collaboration in the reaction Lambda(b) -> J/psi pK might be due to a triangle singularity around the chi(c1)-proton threshold at 4.45 GeV. We discuss the occurrence of a similar triangle singularity in the J/psi p invariant mass distribution for the decay Lambda(b) -> J/psi p pi, which could explain the bump around 4.45 GeV in the data. More precise measurements of this process would provide valuable information towards an understanding of the P-c structures.
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Doring, M., Jido, D., & Oset, E. (2010). Helicity amplitudes of the Lambda(1670) and two Lambda(1405) as dynamically generated resonances. Eur. Phys. J. A, 45(3), 319–333.
Abstract: We determine the helicity amplitudes A(1/2) and radiative decay widths in the transition Lambda(1670) -> gamma Y (Y = Lambda or Sigma(0)). The Lambda(1670) is treated as a dynamically generated resonance in meson-baryon chiral dynamics. We obtain the radiative decay widths of the Lambda(1670) to gamma Lambda as 2 +/- 1 keV and to -gamma Sigma(0) as 120 +/- 50 keV. Also, the Q(2)-dependence of the helicity amplitudes A(1/2) is calculated. We find that the K Xi component in the Lambda(1670) structure, mainly responsible for the dynamical generation of this resonance, is also responsible for the significant suppression of the decay ratio Gamma(gamma A)/Gamma(gamma Sigma 0). A measurement of the ratio would, thus, provide direct access to the nature of the Lambda(1670). To compare the result for the Lambda(1670), we calculate the helicity amplitudes Lambda(1/2) for the two states of the Lambda(1405). Also, the analytic continuation of Feynman parameterized integrals of more complicated loop amplitudes to the complex plane is developed which allows for an internally consistent evaluation of A(1/2).
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PANDA Collaboration(Singh, B. et al), & Diaz, J. (2016). Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR. Eur. Phys. J. A, 52(10), 325–23pp.
Abstract: Simulation results for future measurements of electromagnetic proton form factors at PANDA (FAIR) within the PandaRoot software framework are reported. The statistical precision with which the proton form factors can be determined is estimated. The signal channel (p) over barp -> e(+)e(-) is studied on the basis of two different but consistent procedures. The suppression of the main background channel, i.e. (p) over barp -> pi(+)pi(-), is studied. Furthermore, the background versus signal efficiency, statistical and systematical uncertainties on the extracted proton form factors are evaluated using two different procedures. The results are consistent with those of a previous simulation study using an older, simplified framework. However, a slightly better precision is achieved in the PandaRoot study in a large range of momentum transfer, assuming the nominal beam conditions and detector performance.
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Taprogge, J. et al, Gadea, A., & Montaner-Piza, A. (2016). Proton-hole and core-excited states in the semi-magic nucleus In-131(82). Eur. Phys. J. A, 52(11), 347–10pp.
Abstract: The decay of the N = 83 nucleus Cd-131 has been studied at the RIBF facility at the RIKEN Nishina Center. The main purpose of the study was to identify the position of the and proton-hole states and the energies of core-excited configurations in the semi-magic nucleus In-131. From the radiation emitted following the decay, a level scheme of In-131 was established and the feeding to each excited state determined. Similarities between the single-particle transitions observed in the decays of the N = 83 isotones In-132 and Cd-131 are discussed. Finally the excitation energies of several core-excited configurations in In-131 are compared to QRPA and shell-model calculations.
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