0000000000289565
AUTHOR
T. Wilbois
Relativistic Effects and the Role of Heavy Meson Exchange in Deuteron Photodisintegration
Relativistic effects and the role of heavy meson exchange in deuteron photodisintegration are studied systematically for photon energies below the pion production threshold. In a (p/M)-expansion, all leading order relativistic one-body and pi-exchange as well as all static heavy meson exchange currents consistent with the Bonn OBEPQ model are included. In addition, one- and two-body boost effects have been investigated. Sizeable effects from the various two-body contributions beyond pi-exchange have been found in almost every observable considered, i.e., differential cross section and single polarization observables.
Deuteron Compton Scattering
We have calculated deuteron Compton scattering below pion production threshold using different realistic NN potential models and explicit meson exchange current contributions. The gauge conditions for the current and two photon operators have been exploited extensively, so that our model fulfills the low energy theorems. Rescattering, meson exchange and nucleon substructure contributions are studied and compared with a previous calculation and recent experimental data.
Relativistic effects and spin observables in deuteron electrodisintegration
The influence of relativistic effects in deuteron electrodisintegration, in particular their manifestation in spin observables, is discussed. We have used a simple phenomenological approach by adding the lowest-order relativistic corrections to the nonrelativistic one-body current and including the kinematic wave-function boost. Furthermore, final-state interaction, meson-exchange currents and isobar configurations are included in order to study kinematic regions off the quasi-free case. Sizeable relativistic effects in many observables are found even at low energies.
Relativistic effects in quasifree deuteron electrodisintegration compared to a covariant model
Deuteron disintegration by electrons is calculated in a covariant model for the quasifree region, where final-state interaction and two-body currents can be negiected, and is compared to a phenomenological approach in which one adds to the nonrelativistic one-body current relativistic contributions of lowest order and the kinematic wave-function boost. It is shown that ap/M-reduction of the relativistic theory contains the expressions of the phenomenological approach. The inclusion of relativistic contributions leads to a less frame-dependent description and the deviation from the covariant theory becomes small at low and medium energy and momentum transfers. Furthermore, the dependence of …
Comment on ‘‘Multinucleon mechanisms in (γ,N) and (γ,NN) reactions’’
Recently, calculations of (\ensuremath{\gamma},NN) cross sections in the \ensuremath{\Delta}(1232) region have been reported by J. Ryckebusch et al. [Phys. Rev. C 49, 2704 (1994)]. However, these calculations use an unjustified ansatz for the \ensuremath{\Delta} propagation, which leads to an underestimation of the (\ensuremath{\gamma},NN) cross section in the resonance region for quasifree kinematics. \textcopyright{} 1996 The American Physical Society.
Consistent Treatment of Relativistic Effects in Electrodisintegration of the Deuteron
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…
Separation of theH2(e,e’p) structure functions up to 0.9 GeV/cmomentum transfer
Longitudinal, transverse, and longitudinal-transverse structure functions for the $^{2}\mathrm{H}$(e,e'p) reaction have been determined. Measurements of the cross sections were made in-plane in nearly quasielastic kinematics spanning momentum transfers between 200 and 670 MeV/c and recoil momenta between 0 and 150 MeV/c. In addition, cross sections at momentum transfers above 800 MeV/c were measured at backward scattering angles in aligned kinematics where the response is predominantly transverse. We compared our data with both relativistic and nonrelativistic models. Our results are not consistently in agreement with any of the calculations based on these models. The disagreement between o…