Theoretical calculation of the forward cross section for deuteron photodisintegration up to 120 MeV

The forward differential cross section for γd → pn in the c.m. frame is calculated for laboratory photon energies up to 120 MeV, using the Paris potential and including relativistic corrections to the impulse approximation and the effect of one-pion exchange, with and without Δ(1231) intermediate states. We give a full treatment of one-pion exchange effects and show that the correction due to them is small (except at energies below 20 MeV) and that it can be accurately calculated. We give a consistent relativistic treatment of the two-nucleon system and correct errors in the well-known work of Partovi which arise from his nonrelativistic treatment. It is shown that the calculated cross section is very sensitive to charge-dependent effects in the one-pion exchange part of the nucleon-nucleon potential and that it is possible to obtain reasonable agreement with the present experimental data when the potential used to calculate the T = 1 np wave functions has a one-pion exchange part which takes account of the masses and coupling constants of both neutral and charged pions.     

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)     

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.     

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)     

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.     

Deuteron photodisintegration at high energy

The high-energy two-body deuteron break-up is a very well-suited process to identify quark effects in nuclei. In particular, its study in the few GeV region can clarify the transition from the nucleonic to the QCD picture of hadrons. The CEBAF Large Angle Spectrometer (CLAS) at JLab allowed for the first time the complete measurement of the angular distributions of the two-body deuteron photodisintegration differential cross-section at photon energies from 0.5 to 2.95 GeV. First results from the analysis of 30% of the total collected data show persistent forward-backward asymmetry and are well described by a calculation derived in the non-perturbative framework of the Quark Gluon String Model (QGSM).Received: 30 September 2002, Published online: 22 October 2003PACS: 21.45. + v Few-body systems - 25.20.-x Photonuclear reactionsF. Ronchetti: Present address: Laboratori Nazionali di Frascati, CP 13, Via E. Fermi 40, 00044 Frascati, Roma, Italy     

Photon energy dependence of the differential cross section for atomic-field bremsstrahlung

In a coincidence experiment we have measured the absolute fully differential cross section for atomic-field bremsstrahlung over a range of photon energies for electrons of 140 keV incident on gold and aluminum. The results are compared with the available calculations.     

Proton-nucleus inelastic cross section at ultra high energy

Energy dependence of proton-nucleus reaction cross section at very high energy is discussed. It is stressed that depending on the gluon distribution near the nuclear surface, proton-nucleous total cross section increases much more rapidly compared to the usual Glauber independent nucleon estimate. The recent observation of smaller X _max than the expected value at UHECR domain can be an indication for such a mechanism.     

Total photoproduction cross section at very high energy

In this paper we apply to the photoproduction total cross section a model we have proposed for purely hadronic processes and which is based on QCD mini-jets and soft gluon re-summation. We compare the predictions of our model with the HERA data as well as with other models. For cosmic rays, our model predicts substantially higher cross sections at TeV energies than models based on factorization, but lower than models based on mini-jets alone, without soft gluons. We discuss the origin of this difference.     

The total photon deuteron hadronic cross section in the energy range 0.265–4.215 GeV

The total cross section for photoproduction of hadrons on the deutron, σ_T^d, has been measured for photon energies in the range 0.265–40215 GeV. From this, using results for the photon total cross section, obtained previously with the same apparatus, the neutron total cross section has been determined in the resonance region. The resonant structure is found to be quite different from that for the proton. Thereafter the neutron cross section falls off steadily with energy, and the values obtained are consistently lower than those for the proton. Forward scattering amplitudes have been evaluated for the deuteron.     

Qualitative modification of the high energy atomic photoionization cross section

It is demonstrated that the nonrelativistic high energy omega-->infinity behavior of the photoionization cross section of an nl atomic subshell, sigma(nl)(omega), for l>0 is independent of l and is given by sigma(nl)(omega) approximately 1/omega(9/2), rather than the previously generally accepted sigma(nl)(omega) approximately 1/omega(l+7/2). Furthermore, for l = 1, although the exponent does not change, the coefficient is significantly altered. This modification of sigma(nl)(omega) is due to the interchannel interaction between ns photoionization channels and l not equal0 channels in the atom. As a result, for the photoionization of l not equal0 electrons, the single-particle approximation is never correct in the omega-->infinity limit. This has important consequences for sum rule calculations.     

Target asymmetry measurement of deuteron photodisintegration at a photon energy of 550 MeV

The target asymmetry of the deuteron photodisintegration was measured at a photon energy of 550±50 MeV and at proton center-off-mass angles between 25 and 155 degrees.D-butanol andND ₃ were used as target material yielding a maximum deuteron polarization of 41%. Proton and neutron were detected in coincidence. The data show a structure which cannot be described by the existing analyses.     

The dependence of the photodisintegration cross section on the off-shell T-matrix

Nucleon-nucleon scattering phase shifts determine the diagonal element of the transition matrix. The off-diagonal elements are not completely arbitrary but have conditions imposed on them by the range and the tail of the potential. Electromagnetic interaction can also be used to place restrictions on the off-diagonal elements. We find that the cross section of the deuteron photodisintegration is sensitive to the off-shell transition matrix. The integrated cross section can be varied by as much as 30 % or more, and the matrix element for the El transition by a factor of 2. While the matrix element for the photodisintegration depends on the off-shell elements of the T-matrix, it cannot be used to discriminate between alternative off-shell T-matrices. We have constructed classes of different off-shell T-matrices, which produce identical photo-disintegration cross sections and other two-body scattering and bound-state properties.     

Measurement of the two-body photodisintegration of3He in theΔ(1236) resonance region

The³He(γ, p)d reaction has been measured in the photon energy region between 200 MeV and 450 MeV at proton c.m. angles between 20° and 150°. Protons and deuterons were detected in coincidence with two time-of-flight spectrometers consisting of scintillation counters; both particles were identified and their energies and angles were measured. The angular distributions show a strong forward peak. The differential cross sections fall off with increasing photon energy without showing a significant influence of theΔ resonance.     

Asymptotic form of the high energy photoionization cross section of fullerenes

We show that the theoretical predictions on high energy behavior of the photoionization cross section of fullerenes depend crucially on the form of the function $V(r)$ which approximates the fullerene field. The shape of the high energy cross section is obtained without solving the wave equation. The cross section energy dependence is determined by the analytical properties of the function $V(r)$.     

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.     

Theoretical models for deuteron photodisintegration in the energy range between 250 MeV and 800 MeV

Two theoretical models of γd → pn are developed to study the differential cross-section and'the proton polarization data in a coherent way. The first model is an extension of conventional diagrammatic summations of Born terms and isobar excitation terms. The second model is novel in that the isobar excitation terms are replaced by experimentally determined _γN → N_π helicity amplitudes. The second model allows us to extend to higher energies with the introduction of only one arbitrary parameter. The differential cross-section data are fairly well reproduced in the whole energy range, while the proton polarization data are very far removed from the calculations.