Deuteron Disintegration Research Articles

Quasifree photoabsorption on neutron-proton pairs in 3He

Three-body photodisintegration of 3He is calculated in the photon energy range 200–400 MeV assuming quasifree absorption on np pairs both in initial quasideuteron and singlet configurations. The model includes the normal nucleonic current, explicit meson exchange currents and the Δ(1232)-isobar excitation. The total cross section is increased by a factor of about 1.5 compared with free deuteron photodisintegration. Well below and above the Δ-region also some spin observables differ significantly from the ones of free deuteron disintegration due to the more compressed wave function of the correlated np pairs in 3He compared to the deuteron. The initial singlet state causes a significant change in the analysing power A y . These differences could presumably be seen at the conjugate angles where two-body effects are maximized and where photoreactions could complement similar pion absorption experiments.

Photon absorption on a neutron-proton pair in 3He

The cross section of the reaction 3 He(γ,pn)p spec in the energy range 150–450 MeV has been calculated in a quasifree two-body model and compared with a recent kinematically complete experiment. In comparison with free deuteron disintegration the cross section is increased by a factor of about 1.5, in reasonable agreement with the data for photon energies above 200 MeV. At lower energies the data deviate from the two-body behaviour and thus suggest a more important role of the spectator, requiring a more exact treatment.

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 the nonrelativistic results on the current parametrization, i.e., Dirac-Pauli versus Sachs, is largely eliminated by inclusion of lowest-order relativistic contributions. Results are presented for form factors and structure functions and compared with experimental data for the inclusive reaction.

Neutrino disintegration of deuteron and electromagnetic form factos of neutrinos

We consider disintegration of deuteron by low energy neutrinos or antineutrinos due to their electromagnetic form factors. Effects of magnetic or electric dipole moments, electric charge radii and anapole moments of neutrinos are taken into account.

Forward photodisintegration of the deuteron between 20 and 100 MeV photon energy

Absolute differential cross sections for the forward deuteron disintegration have been determined at photon laboratory energies between 20 and 100 MeV. The statistical uncertainty on the individual results is about ±2.5%, while the overall systematical error amounts to 3%; the angular resolution equals 1.5°. The new CM-frame cross sections are in fair agreement with the predictions from recent theoretical calculations.

Relativistic and meson exchange current effects in few nucleon systems

The Bethe-Salpeter approach is discussed for the A=2 and 3 system. Using a relativistic one boson exchange model the elastic em form factors are calculated. Predictions compare well with the experimental data. Within the same dynamical model fully relativistic meson exchange current contributions are determined and the structure functions for unpolarized deuteron disintegration are studied. Boost effects and the relativistic structure of the nucleon em operators are found to be important in certain kinematic regions. Relativistic corrections to the trinucleon binding energy are discussed using separable representations of the Paris and Bonn potentials.

Anomalous deuteron to hydrogen ratio in naturally occurring fission reactions and the possibility of deuteron disintegration

A hypothesis is presented for explaining the experimentally determined anomalous D/H ratio observed in the samples from the naturally occurring fission reaction in the Oklo phenomenon. No other explanation has been given, to our best knowledge, for the large difference between the measured D/H ratio in the Oklo samples and the expected values in a fission neutron spectrum. A multicomponent system consisting of hydrogen, deuterium, tritium and helium nuclei is considered. An analytical solution is derived and solved using as boundary conditions the experimentally determined value of the D/H ratio. The solution of the rate equations for hydrogen and deuteron concentrations, assuming a pure fission process without a deuteron sink term, yields a D/H ratio of 445 ppm for a reaction in which the fluence of neutrons is 1021 n/cm2. This exceeds the experimentally observed value of 127 ppm, and the naturally occurring value of 150 ppm. Solving the same rate equations accounting for a deuterium sink term using a hypothesis of deuteron disintegration, and the experimentally observed value of 127 ppm yields a deuteron disintegration constant of 7.47·10−14 s−1. Deutron disintegration would provide a neutron source, in addition to the fission neutrons, driving a subcritical chain reaction over an extended period of time. Relationship of the presented hypothesis to the Vlasov theory of an annihilation meteorite impact explosion explaining the experimentally observed anomalous235U/238U ratio, and to the suggestion of deuteron disintegration as a possible explanation of some observations of deuterium dissociation in palladium and titanium electrodes is discussed. The tritium and helium-3 rate equations are further solved under the deuteron disintegration hypothesis and the relationship of the present work to the work by JONES et al. is discussed.

Experiences with bubble detectors in monitoring neutron emission from spent reactor fuel

Bubble damage detectors were investigated as a possible nondestructive tool via neutron detection for in-field safeguards verification of spent fuel. Preliminary analysis of the influence of high gamma intensity and gamma energies above the deuteron disintegration threshold - required by this field of application - was performed under laboratory conditions. The effect of radiation damage on the neutron response proved to be negligible below 5 kGy gamma dose. In-field tests were performed on spent fuel assemblies of a WWR-SM research reactor and a WWER-440 type power station. Whereas the results seem promising, the routine use of this novel method needs some further development work.

Deuteron disintegration in condensed media

We discuss the Oppenheimer-Phillips process as a possible phenomenon leading to deuteron disintegration due to polarization in the Coulomb field of a target nucleus. This reaction may be possible in the context of electrochemically compressed deuterons in a palladium cathode. The process is exothermic and may lead to neutron capture from the deuterons into the palladium isotopes, as well as between the deuterons themselves. In the last case, the equivalent of the proton branch of the D-D fusion reaction occurs in preference to the neutron branch. Such a process could provide a model for the processes involved in the observed energy release and tritium production in conjunction with neutron suppression in recent experiments. Possible interactions with Be and fertile isotopes are discussed in the context of breeding fissile isotopes in subcritical configurations.

Coherent electromagnetic excitation and disintegration of relativistic nuclei passing through crystals

The energy dependence of electromagnetic excitation and electromagnetic disintegration cross sections for relativistic nuclei passing through crystals is investigated both theoretically and by means of computer simulation. For electromagnetic excitation, resonant peaks are found at definite energy values. An increase of electromagnetic excitation and disintegration cross sections in crystals at very high energies is found to be due to coherent addition of amplitudes. Numerical results are presented for the electric dipole excitation of fluorine nuclei and electromagnetic deuteron disintegration.

Hard pion exchange currents and the backward deuteron disintegration

Relation between exchange currents and a potential is discussed in the framework of the Schroedinger-like scheme. Backward deuteron disintegration is studied using the Paris and Reid soft-core potentials and the static hard pion exchange currents up to the order ▪

On the Possibility of Deuteron Disintegration in Electrochemically Compressed D+in a Palladium Cathode

The possibility of deuteron disintegration due to polarization in the coulomb field of a target nucleus according to an Oppenheimer-Phillips process is discussed within the context of electrochemically compressed D+ in a palladium cathode. This reaction is possible between deuterons and palladium isotopes, as well as between the deuterons themselves. In the last case, the equivalent of the proton branch of the deuterium-deuterium fusion reaction occurs in preference to the neutron branch. The process provides a possible explanation for the observed energy release, tritium production, and neutron suppression in the Fleischmann and Pons experiment. If such a process can be experimentally verified, analogous processes leading to the disintegration of the 9Be nucleus may be achievable.

Polarisation effects in deuteron electrodisintegration and the neutron electric form factor

The polarisation effects sensitive to the neutron electric form factor GEn in deuteron electrodisintegration are analysed using the relativistic impulse approximation. The authors consider the scattering of longitudinally polarised electrons by a vector-polarised deuteron target. The high-energy neutrons (detected in coincidence with scattered electrons) are emitted along the virtual photon momentum k. In this case the target polarisation should be orthogonal to k and must lie (in coplanar geometry) in the gamma *d to np reaction plane, gamma * being the virtual photon. If the target polarisation is orthogonal to the reaction plane, then in order to determine GEn, it is necessary to study the phi dependence of the corresponding asymmetry. Some polarisation components of high-energy neutrons produced in disintegration of unpolarised deuterons by longitudinally polarised electrons are also sensitive to GEn.

Chiral and relativistic effects in backward deuteron disintegration

The backward deuteron disintegration is studied within the gauge chiral scheme containing ,π and A 1 mesons. The effects due to other heavy meson exchanges (ω,δ,η,σ) present in the Bonn potential are also considered. The leading relativistic corrections to the currents are derived in the framework of the modified S-matrix method.

Neutron electric form factor in inelastic scattering of polarized electrons by polarized deuterons

The asymmetries for the disintegration of vector-polarized deuterons by longitudinally polarized electrons are calculated. The sensitivity to the neutron electric form factor and the deuteron wave function is discussed.

Deuteron disintegration by polarized electrons and the electric form factor of the neutron

The electron polarization asymmetry ∑ e for d( e , e′n)p using longitudinally polarized electrons is studied in the quasi free region with specific emphasis on the influence of the neutron electric form factor. Sizeable effects are found for neutrons emitted in the forward direction with respect to the momentum transfer. Since, however, the potential model dependence of ∑ e is of the same size, a very good knowledge of the NN interaction is required for the extraction of the neutron electric form factor.

Proton polarization in deuteron disintegration by linearly polarized photons and dibaryon resonances

The paper deals with proton polarization measurements in the deuteron disintegration γd → pn by linearly polarized photons and a theoretical description of the measured data on differential cross sections with unpolarized particles (dσ/dΩ) 0, the asymmetry due to the photon linear polarization Σ, the proton polarization P y , and the asymmetry due to the deuteron vector polarization T. At E γ = 300, 350, 400, 500 MeV and θ = 90° (θ being the angle between the c.m.s. proton and photon momenta), under the same experimental conditions, Σ, P y and the double-polarization observable, viz the T 1, asymmetry of the proton polarization with linearly polarized photons, are obtained. It is shown that the model without dibaryons fails to provide a satisfactory description of the collection of experimental data on ( dσ/ dΩ) 0, Σ, P y, T in the photon energy range between 160 and 400 MeV. The consideration of unit-isospin dibaryons 1 D 2(J π = 2 +), 3 F 3(J π = 3 −), 1 S 0(J π = 0 +), 3 P 1(J π = 1 −) essentially improves the agreement with experiment.

Quantum-field aspects of pion interaction with lightest nuclei

Recent development in the quantum field theory approach to the pion-deuteron and pion-aHe (3 H)-interaction processes is reviewed. Some general features of the Bethe-Salpeter and Low-type equations for the processes under study derived in the last few years in the literature are discussed. At present the fundamental importance of studying the pion-deuteron or more generally the pion -- two-nucleon interaction is well understood. The nNN system is often considered as a "theoretical laboratory" for investigating different aspects of the pion-nucleus interaction. In the first stage of investigation of pion-deuteron scattering, carried out predominantly in the energy range 0--300 MeV, the multiple scattering theory has been used, where the many-channel character of the problem is neglected, particularly, the deuteron disintegration channel and the channel of pion absorption by a deuteron are neglected. The necessity of the account of such channels and relativity of pions in the energy region under consideration leads to the use of Faddeev integral equations or their generalization in the case where the relativistic kinematics of pions and pion absorption or emission by a two-nucleon system are taken into account. This type of the theory [1, 2] for the coupled nNN and NN-systems formulated in the framework of the general coupled channel theory for the pion-nucleous interaction [3] by using the projection operator method [4] is expounded (with some generalization) in [5], where other references to the subject can be found. As regards the problem of pion interaction with the simplest (after deuteron) nuclei SHe and 3H from the theoretical point of view it is primarily interesting as a tool for verifying an understanding of the dynamics of the pion-nucleus interaction resulting from an investigation of the pion two-nucleon interaction. But it is clear that study of the zc 3He(3H)-interaction per se is also interesting not only for understanding the dynamics of these processes but to get additional information on the three-nucleon forces. In [6] a successful attempt was made to generalize the multichannel theory of nNN and NN systems [1, 2] to the case of pion interaction with the 3Henucleus. It is worth-while to note that in spite of a sufficient generality of these considerations the antiparticle degree of freedom is neglected and the crossing symmetry of the problem is not taken into account. The importance of allowing for this symmetry was demonstrated in [7] taking ~-12C-scattering at low energies as an example. As to the nN-scattering, the importance of allowing for crossing-symmetry is well known from the Chew-Low theory [8]. The two aforementioned effects are of quantum-field origin and therefore can be taken into account in the framework of the quantum field theory approach to the problem. Some general results obtained using this approach are discussed below. A consistent quantum-field theoretical approach was used in [2] to derive a set of equations for the reactions

Kaon-induced deuteron disintegration with two-body final states

Integrated cross sections for the reactions K −d → Σ −p and K −d → Λn have been obtained within a simple model that involves excitation of an S = − l, I = 0 or 1 resonance (Y ∗) followed by a pseudoscalar meson exchange that deexcites the resonance and transfers momentum to the other nucleon. The model incorporates the eight well-established Y ∗ below 1700 MeV with coupling strengths estimated from partial decay widths and SU(3) symmetry relations. Initial-state correlations are included through the deuteron wave function, obtained with the Reid NN interaction, while final-state correlations are ignored. When examined as functions of the laboratory kaon momentum, the cross sections computed with form factors omitted exhibit two prominent features: a narrow structure centred at 385 MeV/ c, due almost entirely to Λ(1520) excitation, and a broader peak around 700 MeV/ c, that is associated with several overlapping resonances above 1650 MeV. In principle, these two structures could provide coupling-strength information within a more quantitative model. Both peaks are quite sensitive to the inclusion of form factors, however, and may be difficult to detect if the phenomenologically required form factors are as long-ranged as the sparse data presently available indicate.

Deuteron photodisintegration. I. Theory and results at low energies

We extend the “elementary-particle treatment” of deuteron electrodisintegration at small excitation energies, as recently developed by Hwang, Henley, and Miller, by incorporating more ( np)-scattering states so that deuteron disintegration by low-energy photons (e.g., ≤150 MeV) can also be investigated. As compared to the well-known formalism obtained by Partovi, the present theory has the following distinct features: The nucleon-only impulse approximation (NOIA), as modified to incorporate gauge invariance (GI), is assumed to be valid only in the Breit frame, in which the initial and final nuclear systems are treated symmetrically. The matrix element of the electromagnetic current is thus determined in the Breit frame and then transformed into the CM frame (i.e., the rest frame for the final n + p, or initial γ + D, system). In addition, the difference between the resultant NOIA GI and the NOIA is determined explicitly in every channel. Numerical results are obtained for the Reid soft-core potential with extensions required for J > 2 scattering states. Our major result is that there is no substantial discrepancy between the θ p = 0° data of Hughes et al. and the prediction of this formalism. General features of this formalism, including angular distributions at low energies, are discussed in quantitative terms. Other important results at these energies include: (1) the 3F J(np) -scattering states are found to be important for E γ ≥ 20 MeV, especially at forward and backward angles (i.e., θ p ∼ 0° or 180°); (2) the meson-exchange currents arising from intermediate isobar |Δ(1232)| propagation, with or without energy transfer effects, are not yet of any numerical significance; and (3) the results exhibit sensitivity to details of final-state interactions.