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80 - V. Shklyar , H. Lenske , U. Mosel 2014
We present a coupled-channel Lagrangian approach (GiM) to describe the $pi N to pi N$, $2pi N$ scattering in the resonance energy region. The $2pi N$ production has been significantly improved by using the isobar approximation with $sigma N$ and $pi Delta(1232)$ in the intermediate state. The three-body unitarity is maintained up to interference pattern between the isobar subchannels. The scattering amplitudes are obtained as a solution of the Bethe-Salpeter equation in the $K$ matrix approximation. As a first application we perform a partial wave analysis of the $pi N to pi N$, $pi^0pi^0 N$ reactions in the Roper resonance region. We obtain $R_{sigma N}(1440)=27^{+4}_{-9}$,% and $R_{sigma N}(1440)=12^{+5}_{-3}$,% for the $sigma N$ and $pi Delta$ decay branching ratios of $N^*(1440)$ respectively. The extracted $pi N$ inelasticities and reaction amplitudes are consistent with the results from other groups.
The results of the microscopic transport calculations of $bar p$-nucleus interactions within a GiBUU model are presented. The dominating mechanism of hyperon production is the strangeness exchange processes $bar K N to Y pi$ and $bar K N to Xi K$. Th e calculated rapidity spectra of $Xi$ hyperons are significantly shifted to forward rapidities with respect to the spectra of $S=-1$ hyperons. We argue that this shift should be a sensitive test for the possible exotic mechanisms of $bar p$-nucleus annihilation. The production of the double $Lambda$-hypernuclei by $Xi^-$ interaction with a secondary target is calculated.
119 - V. Shklyar , H. Lenske , U. Mosel 2012
We perform an updated coupled-channel analysis of eta-meson production including all recent photoproduction data on the proton. The dip observed in the differential cross sections at c.m. energies W=1.68 GeV is explained by destructive interference b etween the $S_{11}(1535)$ and $S_{11}(1560)$ states. The effect from $P_{11}(1710)$ is found to be small but still important to reproduce the correct shape of the differential cross section. For the $pi^- N to eta N$ scattering we suggest a reaction mechanism in terms of the $S_{11}(1535)$, $S_{11}(1560)$, and $P_{11}(1710)$ states. Our conclusion on the importance of the $S_{11}(1535)$, $S_{11}(1560)$, and $P_{11}(1710)$ resonances in the eta-production reactions is in line with our previous results. No strong indication for a narrow state with a width of 15 MeV and the mass of 1680 MeV is found in the analysis. $eta N$ scattering length is extracted and discussed.
161 - N. Tsoneva , H. Lenske 2009
We present recent investigations on dipole and quadrupole excitations in spherical skin nuclei, particular exploring their connection to the thickness of the neutron skin. Our theoretical method relies on density functional theory, which provides us with a proper link between nuclear many-body theory of the nuclear ground state and its phenomenological description. For the calculation of the nuclear excited states we apply QPM theory. A new quadrupole mode related to pygmy quadrupole resonance (PQR) in tin isotopes is suggested.
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