Search results for "Body system"
showing 10 items of 67 documents
Three-body resonances in two-meson-one-baryon systems
2007
We report four $\Sigma$'s and three $\Lambda$'s, in the 1500 - 1800 MeV region, as two meson - one baryon S-wave $(1/2)^+$ resonances. We solve Faddeev equations in the coupled channel approach. The invariant mass of one of the meson-baryon pairs and that of the three particles have been varied and peaks in the squared three body $T$-matrix have been found very close to the existing $S$ = -1, $J^P= 1/2^+$ low lying baryon resonances. The input two-body $t$-matrices for meson-meson and meson-baryon interaction have been calculated by solving the Bethe-Salpeter equation with the potentials obtained in the chiral unitary approach.
Two-body effects in coherent η-meson photoproduction on the deuteron in the region of theS11(1535)resonance
2001
Coherent \ensuremath{\eta}-meson photoproduction on the deuteron has been studied, where the emphasis is on the relative importance of two-body contributions from hadronic rescattering and electromagnetic meson exchange currents besides the impulse approximation. For the elementary photoproduction amplitude a coupled resonance model developed by Bennhold and Tanabe has been used that fits reasonably well with the experimental data. The rescattering effects are treated within a coupled channel approach considering the intermediate excitation of the ${P}_{11}(1440),$ ${D}_{13}(1520),$ and ${S}_{11}(1535)$ nucleon resonances. The hadronic interaction between nucleon and resonances is modeled b…
Consistent Treatment of Relativistic Effects in Electrodisintegration of the Deuteron
1996
The influence of relativistic contributions to deuteron electrodisintegration is systematically studied in various kinematic regions of energy and momentum transfer. As theoretical framework the equation-of-motion and the unitarily equivalent S-matrix approaches are used. In a (p/M)-expansion, all leading order relativistic $\pi$-exchange contributions consistent with the Bonn OBEPQ model are included. In addition, static heavy meson exchange currents including boost terms, $\gamma\pi\rho/\omega$-currents, and $\Delta$-isobar contributions are considered. Sizeable effects from the various relativistic two-body contributions, mainly from $\pi$-exchange, have been found in inclusive form fact…
Nucleon polarization in exclusive deuteron electrodisintegration with polarized electrons and a polarized target
1995
Nucleon polarization in exclusive electrodisintegration of the deuteron using a polarized beam and an oriented target is systematically investigated in a nonrelativistic framework but with lowest order relativistic contributions to the one-body current including the kinematic part of the wave function boost. The structure functions and the asymmetries corresponding to the various nucleon polarization components are studied with respect to their sensitivity to the potential model, to subnuclear degrees of freedom, and to relativistic effects in different kinematical regions. Furthermore, a few new observables are found which are very sensitive to the neutron electric form factor ${\mathit{G}…
Low-energy scattering and photoproduction ofηmesons on three-body nuclei
2003
The optical potential approach for low-energy scattering of $\eta$-mesons on three-body nuclei is compared to an exact treatment of the $\eta 3N$ system using four-body scattering theory with separable interactions in s-waves only. The higher-order terms including the interaction of the struck nucleon with the surrounding nuclear medium and virtual target excitations in between successive $\eta$-scatterings are found to cause important corrections. Effects of final state interaction in $\eta$-photoproduction on $^3$H and $^3$He are also studied and sizable contributions beyond the optical model approach are found.
Incoherent pion photoproduction on the deuteron with polarization observables I: Formal expressions
2005
Formal expressions are developed for the general five-fold differential cross section of incoherent $\pi$-photoproduction on the deuteron including beam and target polarization. The polarization observables of the cross section are described by various beam, target and beam-target asymmetries for polarized photons and/or polarized deuterons. They are given as bilinear hermitean forms in the reaction matrix elements divided by the unpolarized cross section. In addition, the corresponding observables for the semi-exclusive reaction $\vec d(\vec \gamma,\pi)NN$ are also given.
Incoherent pion photoproduction on the deuteron with polarization observables II: Influence of final state rescattering
2005
Incoherent pion photoproduction on the deuteron is studied for photon energies from threshold up to 1 GeV with special emphasis on polarization observables. The elementary $\gamma N\to\pi N$ amplitude is taken from the MAID model. The influence of final state interactions on total and semi-exclusive cross sections $\vec d(\vec\gamma,\pi)NN$ is investigated by including complete rescattering in the final $NN$- and $\pi N$-subsystems. For charged pion-production the influence of $NN$-rescattering is moderate whereas $\pi N$-rescattering is almost negligible. Much stronger influences of $NN$-rescattering are seen in neutral pion production, which is due to the elimination of a significant spur…
Isospin dependence of the three-nucleon force
2004
We classify $A$--nucleon forces according to their isospin dependence and discuss the most general isospin structure of the three--nucleon force. We derive the leading and subleading isospin--breaking corrections to the three--nucleon force using the framework of chiral effective field theory.
Photon absorption on a proton-proton pair inHe3
1995
We calculate the total cross sections for different multiple transitions in photon absorption in a {sup 1}{ital S}{sub 0} {ital pp} pair embedded in a {sup 3}He nucleus. Employing two models, one involving only nucleon degrees of freedom, the other in addition the {Delta}(1232) isobar, we show that the {Delta} gives important effects even in transitions where the photon cannot couple directly to the isobar.
Binding of charmonium with two- and three-body nuclei
2006
The energies of the (eta_c d) and (eta_c 3He) bound states are calculated on the basis of exact three- and four-body AGS equations. For the eta_c N interaction a Yukawa-type potential has been adopted. The calculations are done for a certain range of its strength parameter. The results obtained are quite different from calculations based on the folding model.