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.     

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 nonconservation in the deuteron photodisintegration

We calculate P-odd difference of the total cross sections of the deuteron disintegration by left and right polarized photons. The relative magnitude of this difference in the threshold region is about 10⁻⁷. Its experimental measurement would give valuable information on the weak nucleon–nucleon interaction at short distances.     

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     

Meson-retardation effects in deuteron photodisintegration below π-threshold

Mesor-retardation effects in photodisintegration of the deuteron below pion threshold are studied by constructing retarded one-boson-exchange potentials using time-dependent non-covariant perturbation theory. The corresponding retarded meson-exchange currents including retarded vertex currents are derived analogously by gauge-invariant minimal coupling. It is found that retardation effects in the wave functions and in the electromagnetic currents as well have a significant influence on total and differential cross sections.Supported by the Deutsche Forschungsgemeinschaft (SFB 201)     

Measurement of tensor analyzing powers in deuteron photodisintegration

A new accurate measurement of the tensor analyzing powers T20, T21, and T22 in deuteron photodisintegration has been performed. Wide-aperture nonmagnetic detectors allowed broad kinematic coverage in a single set up: E(gamma)=25 to 600 MeV, and theta(p)(cm)=24 degrees to 48 degrees and 70 degrees to 102 degrees . The new data provide a significant improvement over the few existing measurements. The angular dependency of the tensor asymmetries in deuteron photodisintegration is extracted for the first time.     

Survey on polarization observables in deuteron photodisintegration below pion-production threshold

Polarization observables of deuteron photodisintegration with polarized photons and oriented deuterons are systematically investigated below -production threshold with respect to their sensitivity to subnuclear degrees of freedom and relativistic effects, to the different electric and magnetic multipole contributions, and to various realistic potential models. In particular, a complete survey on all single- and double-polarization observables like beam and target asymmetries of the differential cross section, nucleon polarization and proton-neutron spin correlation is given.Partially supported by the Deutsche Forschungsgemeinschaft (SFB 201)     

Experimental investigation of deuteron photodisintegration in the δ-resonance region

Differential cross sections for the deuteron photodisintegration process were measured for photon energies between 200 and 440 MeV using the tagged photon beam facility of the Bonn 500 MeV synchrotron. At eight angles between 18° and 145° charged particles were detected simultaneously in time-of-flight spectrometers consisting of scintillation counters. Above the resonance region the measured cross sections agree fairly well with earlier results, whereas there are larger discrepancies at low photon energies.     

Pauli anisotropy in high-energy deuteron scattering

Antisymmetrization of the deuteron-nucleus system leads to an effective three-body interaction that is quadrupole in the neutron-proton displacement vector. This can cause anisotropic deuteron breakup or polarization of scatered deutrons. The effect is largest at about 100 MeV. A relation to work by Ioanides and Johnson is indicated.     

Dependence of forward deuteron photodisintegration on the D state

The cross section for forward produced protons in deuteron photodisintegration is shown to be moderately sensitive to the % D state of the deuteron. A 4.58% D state model has about half the discrepancy from experiment of a 7.53% model.     

General formulae for polarization observables in two-body break-up of deuteron photodisintegration

The formal expressions of all possible polarization observables ind(,N)N with polarized photons and oriented deuterons are derived in terms of thet-matrix elements. Furthermore, using the multipole expansion of thet-matrix, all observables are expanded in terms of Legendre polynomials or associated functions, the coefficients of which are given as bilinear forms of the multipole moments and allow a model independent analysis of experimental data.Supported by the Deutsche Forschungsgemeinschaft (SFB 201)     

Cross-section asymmetry in the photodisintegration of the deuteron by polarized photons

The asymmetry of cross sections for the photodisintegration of the deuteron has been measured in the linearly polarized photon energy range 80–600 MeV at c.m. proton emission angles 75°–150°. The obtained data are not found to be in agreement with theoretical predictions.     

Relations between polarization observables and complete sets for deuteron photodisintegration

The polarization observables for deuteron photodisintegration are given as Hermitean forms of theT-matrix elementst _i . By inversion we are able to express a given productt _i ^* t _j in terms of polarization observables. This allows (i) to derive linear relations between observables for unpolarized, circularly and linearly polarized photons, (ii) to construct explicitly complete sets of polarization observables, and (iii) to derive quadratic relations between observables.Supported by the Deutsche Forschungsgemeinschaft (SFB 201)     

Polarization transfer in deuteron stripping reactions

Polarization phenomena involving the spins of a and b in the A(a, b)B reaction are discussed using a complete set of irreducible tensors carrying definite spin transfer. The linear model independent equations relating the cross section and the polarization observables with these tensors are shown to be particularly appropriate for the study of spin dependent interactions, preferentially associated with particular values of spin transfer. The DWBA theory of polarization transfer in deuteron stripping reactions is thoroughly discussed and among the 17 polarization observables we distinguish those likely to be more sensitive to spin dependent distortion, to have stronger deuteron D-state effects, to exhibit the sign-rule j-dependence and other forms of j-dependence. For certain deuteron polarizations, when the spin transfer is pure $\text{s =}\text{1}\text{2}$, it is shown that deuteron stripping reactions are transparent to vector polarization transfer and the outgoing nucléon polarization independent of scattering angle and deuteron energy. DWBA calculations including contributions from spin transfer $\text{3}\text{2}$ through the deuteron D-state and spin-orbit distortion show that polarization transfer in such deuteron polarizations can be explored as a method of producing fast polarized neutrons with known polarization.     

Forward photodisintegration of the deuteron at 10.74 MeV photon energy

The absolute differential cross section for the photodisintegration of the deuteron at 0° for the outgoing proton has been measured at 10.74 MeV lab photon energy using a bremsstrahlung beam, a deuterated target, a magnet system, and a surface barrier detector. The absolute cross section is (4.7±0.85) b/sr and was determined with an angular resolution of 1.25°. The result, pertaining to a 4.6 MeV wide photon energy interval, favours a minimum in the differential cross section around 10 MeV photon energy.Supported in part by the Deutsche Forschungsgemeinschaft (SFB 201)     

Consistent treatment of relativistic corrections in deuteron photodisintegration in a one-pion-exchange model

Using a one-pion-exchange model for the nucleon-nucleon interaction the relativistic corrections to potential and to the electromagnetic operators are derived in a power expansion of (p/M). All corrections up to the order (p/M)³ are consistently included. Numerical results are shown for differential cross section and polarization observables for deuteron photodisintegration. A sizeable influence of relativistic effects on some observables is found even at low energies. A comparison of our operators with the expressions of other authors is given.Supported by Deutsche Forschungsgemeinschaft (SFB 201)