Elastic and inelastic scattering of high-energy particles on the deuteron

The scattering amplitudes on the deuteron at small momentum transfers are described, taking into account the shadow corrections. In the framework of Regge pole theory, the inelastic shadow corrections are expressed in terms of the amplitudes of inelastic processes. The validity limit of the formulae thus obtained is discussed.     

Polarization measurements in high-energy deuteron photodisintegration

We present measurements of the recoil proton polarization for the d(gamma-->,p-->)n reaction at straight theta(c.m.) = 90 degrees for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization p(y) vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer Cx does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the d(gamma,p)n cross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime.     

Elastic electron deuteron scattering

Measurements of the ratio of the deuteron to proton electric form factors were made for low q. The rms radius of the deuteron structure factor was found to be 1.9635 ± 0.0045 fm, yielding an rms charge radius of 2.095 ± 0.006 fm.     

Forward-backward angle asymmetry and polarization observables in high-energy deuteron photodisintegration

Deuteron two-body photodisintegration is analysed within the framework of the Quark-Gluon Strings Model. It is found that the forward-backward angle asymmetry predicted by the model is confirmed by the recent data at different photon energies from JLab. New calculations for polarization observables, the cross-section asymmetry and the polarization transfer , for photon energies GeV are presented and compared with the data available up to 2 GeV.Received: 7 July 2003, Published online: 26 November 2003PACS: 13.40.-f Electromagnetic processes and properties - 25.20.-x Photonuclear reactions     

Parity-violating effects in elastic electron deuteron scattering

The general expressions for parity violation observables in elastic scattering of polarized and/or unpolarized electrons from unpolarized deuterons are given and are numerically evaluated for the kinematics of SAMPLE, PVA4 and G0 experiments. The dominant contribution from the interference of and Z exchange as well as the smaller contributions from strangeness (s components of the nucleon, parity odd admixtures in the deuteron wave function, anapole moments and radiative corrections are included and discussed in the context of parity-violating electron scattering experiments of present interest.     

Recoil-proton polarization in high-energy deuteron photodisintegration with circularly polarized photons

We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.     

Polarization effects in elastic electron deuteron scattering

The vector and tensor polarization of the deuteron after scattering and the dependence of the cross section on the polarization before scattering are given for elastic electron deuteron scattering treating the deuteron as a spin 1 elementary particle characterized by three electromagnetic formfactors and describing the interaction by the first Born approximation. By using polarization measurements a separation of the charge and quadrupole formfactors may be accomplished, and thus the assumptions may be tested, which are necessary for the extraction of the isoscalar nucleon formfactors from the deuteron formfactors.     

Thermodynamical approach in high-energy scattering

A non-conventional thermodynamical approach earlier for high-energy collisions is considered in more detail. The approach provides a physical interpretation not only of the shape of the hadron form factor but also of the increase in its radius with energy . A precise analysis of experimental data on elastic scattering for is performed with the formulae derived. Predictions in the multi TeV range and comparison of results with recent data of the E 710 Collaboration for 1.8 TeV are made. Agreement occurs when the experimental t-distribution is scaled up by 11%.     

Off-shell effects in scattering from the deuteron

A simple model for scattering from a deuteron is studied. Within this model exact coupled channel solutions, including all multiple scattering series terms, are obtained for a fixed separation of the two scattering potentials. These solutions are compared with approximations which involve a spherically averaged or non-overlapping potential. Our results indicate that the non-negligible contributions arising from the overlapping potential region can be adequately reproduced by a combination of simple approximations thereby facilitating calculations of scattering from a more physical deuteron model.     

Parity violation in polarised electron deuteron scattering

Preliminary calculations show that the parity violating asymmetry in polarised electron deuteron elastic scattering can be as large as observed in the SLAC experiment even in the intermediate energy region. We propose that experiments should be done to search for these asymmetries.     

Coulomb-nuclear interference for inelastic deuteron scattering

The interference between Coulomb excitation and nuclear excitation has been observed for ^{54, 56}Fe, ⁶⁰Ni, ¹¹⁴Cd, ¹⁵²Sm, and ¹⁹²Os by measuring excitation functions of elastic and inelastic deuteron scattering at back angles. The interference is strongly constructive, indicating a predominantly imaginary nuclear form factor. DWBA calculations using the collective model, although predicting constructive interference, are unable to predict the magnitude of the observed effect.     

Polarization observables in high-energy deuteron photo-disintegration within the Quark-Gluon Strings Model

Deuteron two-body photodisintegration is analysed within the framework of the Quark-Gluon Strings Model. The model describes fairly well the recent experimental data from TJNAF in the few GeV region. Angular distributions at different -energies are presented and the effect of a forward-backward asymmetry is discussed. New results from the QGSM for polarization observables from 1.5-6 GeV are presented and compared with the available data.Received: 30 September 2002, Published online: 22 October 2003PACS: 13.40.-f Electromagnetic processes and properties - 25.20.-x Photonuclear reactions     

Exchange effects in photon scattering off the deuteron

Detailed calculations of elastic photon-deuteron scattering cross sections for photon energies up to about the π-production threshold are presented. The scattering amplitude is decomposed into scalar, vector and tensor polarizabilities for the various electric and magnetic multipole combinations. This includes a general multipole expansion of the two-photon operator. The imaginary part of the polarizabilities is determined from the contribution to the total cross section using the optical theorem. The real part is then obtained from dispersion relations. Special emphasis is laid on the discussion of exchange effects for both the resonance and the two-photon amplitude. These affect strongly the resonance amplitude whereas for the two-photon amplitude we find only a small effect beyond the important low-energy limit. Another important result is the large vector polarizability at higher energies related to the optical activity of the deuteron.     

Pion exchange currents in elastic electron deuteron scattering

The effects of pion-exchange pari and recoil currents on the electromagnetic form factors of the deuteron are calculated. Both exchange currents give significant contributions to the charge form factor and, despite some cancellation, their net effect is appreciable for q² ? 10 fm^?2.     

Non-eikonal effects in high-energy scattering IV. Inelastic scattering

We calculate amplitudes of inelastically scattered high-energy projectiles. For the example of scattering on ¹²C (T_p = 1 GeV) we demonstrate sizeable non-eikonal corrections in diffraction extrema even for relatively small q². At least part of the anomaly in the 3-distribution may be due to these non-eikonal effects.     

Scaling laws in high-energy electron-nuclear scattering

The approximate scaling behavior suggested by recent measurements of electron scattering form factors and inelastic structure functions of few-body nuclei (mass 2, 3, 4) is discussed in a relativistic impulse approximation model. The model is a straightforward extension incorporating spin of a nucleon parton model introduced in recent works. We present results for electric and magnetic form factors as well as inelastic structure functions near threshold. The important corrections to scaling which are present in the preasymptotic regions are found to be well accounted for by the type of binding effects included in the phenomenologically constructed infinite-momentum frame nuclear wave functions. While predicted form factors are very sensitive to the parameters in the wave functions it does not appear possible to associate unambiguous dynamical meaning to these parameters. We find that spin effects bring significant and useful corrections.     

Self-consistency requirement in high-energy nuclear scattering

Practically all serious calculations of exclusive particle production in ultrarelativistic nuclear or hadronic interactions are performed in the framework of Gribov-Regge theory or the eikonalized parton model scheme. It is the purpose of this paper to point out serious inconsistencies in the above-mentioned approaches. We demonstrate that requiring theoretical self-consistency reduces the freedom in modeling high-energy nuclear scattering enormously, and we introduce a fully self-consistent formulation of the multiple-scattering scheme in the framework of a Gribov-Regge--type effective theory. In addition, we develop new computational techniques which allow for the first time a satisfactory solution of the problem in the sense that calculations of observable quantities can be done strictly within a self-consistent formalism.     

The concept of a Pauli barrier in nucleus-nucleus scattering

The influence of partly Pauli-forbidden states on the width of resonances is stuied in the context of the fish bone optical model. A numerical study of α-α and α-¹⁶O scattering shows that the part of the nonlocal interaction of the model which is due to the partly forbidden states represents a Pauli barrier which inhibits transitions between the inner and asymptotic regions and increases the lifetime of resonances.