Intermediate Energy Region Research Articles

中高エネルギー領域における中性子、陽子、光子入射核分裂反応断面積の統一的記述

中高エネルギー領域における中性子、陽子、光子入射核分裂反応断面積の統一的記述

In memory of Paco Ynduráin: A precise determination of ππ scattering from experiment and dispersion relations

This talk is dedicated to the memory of Paco Yndurain, the original speaker in the conference. After a short account of his scientific career, we briefly review our ongoing collaboration to determine precisely the pi pi scattering amplitude including the most recent data by means of Forward Dispersion Relations and Roy Equations. A remarkable improvement in precision over the intermediate energy region is obtained by using once-subtracted Roy Equations in addition to the standard twice-subtracted ones.

Double excitation of helium in collisions with proton and antiproton impact in the energy range 50–500 keV

Double-electron excitation processes of helium atoms by proton and antiproton impact have been theoretically investigated using the four-body formalism of boundary corrected continuum intermediate state (BCCIS-4B) approximation in the energy range of 50–500 keV. In this formalism, the presence of the projectile in the exit channels is described by distorting the final bound state wave functions with coulomb waves (associated with the projectile–electron interactions). The results are in good agreement with the other theoretical and experimental results. Reasonably better agreements have been found in the intermediate and high energy regions. Contributions to the cross section of the different magnetic sub-shells are also analysed.

Distributions of products of the quasifree knocking-out reaction (p, p′n) on halo nuclei in the intermediate-energy region

Expressions for the distribution functions of products of the reaction (p, p′n) of valence neutron knocking-out from halo nuclei were derived using space-time correlation functions. The possibility of using this reaction to study the neutron halo structure was analyzed.

Polarization characteristics of nuclear quasi-free (p, dπ+) reaction

Nuclear reaction 16O(p, dπ+)15N is considered theoretically as a prototype of a specific class of nuclear quasi-free processes where deuteron, α-particle, 3H- or 3He-cluster are produced together with pion or η-meson in proton-nucleus interactions in the intermediate energy region.

Exponentially modified QCD coupling

We present a specific class of models for an infrared-finite analytic QCD coupling, such that at large spacelike energy scales the coupling differs from the perturbative one by less than any inverse power of the energy scale. This condition is motivated by the Institute for Theoretical and Experimental Physics operator product expansion philosophy. Allowed by the ambiguity in the analytization of the perturbative coupling, the proposed class of couplings has three parameters. In the intermediate energy region, the proposed coupling has low loop-level and renormalization scheme dependence. The present modification of perturbative QCD must be considered as a phenomenological attempt, with the aim of enlarging the applicability range of the theory of the strong interactions at low energies.

SUf(3)-symmetry breaking effects of theB→Ktransition form factor in the QCD light-cone sum rules

We present an improved calculation of the B{yields}K transition form factor with a chiral current in the QCD light-cone sum rule approach. Under the present approach, the most uncertain twist-3 contribution is eliminated. And the contributions from the twist-2 and the twist-4 structures of the kaon wave function are discussed, including the SU{sub f}(3)-breaking effects. One-loop radiative corrections to the kaonic twist-2 contribution together with the leading-order twist-4 corrections are studied. The SU{sub f}(3)-breaking effect is obtained, (F{sub +}{sup B{r_reversible}}{sup K}(0)/F{sub +}{sup B{r_reversible}}{sup {pi}}(0))=1.16{+-}0.03. By combining the light-cone sum rule results with the newly obtained perturbative QCD results that have been calculated up to O(1/m{sub b}{sup 2}) by Wu, Huang, and Fang [Eur. Phys. J. C 52, 561 (2007)], we present a consistent analysis of the B{yields}K transition form factor in the large and intermediate energy regions.

α Clustering in the scattering of particles and light atomic nuclei on nuclei

The cluster models now used for the description of light, medium, and heavy nuclei are reviewed. It is shown that the α-cluster model describes various characteristics of light nuclei. On the basis of the theory of multiple diffraction scattering and the α-cluster model with dispersion, an approach making it possible to describe the characteristics observed for the elastic scattering of particles and light nuclei by light α-cluster nuclei in the intermediate-energy region is considered. The differential cross sections and polarization observables calculated on the basis of such an approach are presented for particles and light nuclei elastically scattered by light α-cluster nuclei. These results show that the α-cluster model makes it possible to explain various experimental data on the scattering of intermediate-energy particles on nuclei.

中高エネルギー領域における中性子、陽子、光子入射核分裂反応断面積の統一的記述（１）概要および実験データの現状

中高エネルギー領域における中性子、陽子、光子入射核分裂反応断面積の統一的記述（１）概要および実験データの現状

Criticality of a 237Np Sphere

A series of critical-mass experiments using a 6-kg neptunium sphere was performed on the Planet vertical-assembly machine at Los Alamos National Laboratory (LANL). The purpose of the experiments was to obtain a better estimate of the critical mass of 237Np. The configurations that were studied included surrounding the neptunium sphere with highly enriched uranium (HEU) shells as well as reflecting it with iron and polyethylene. An additional experiment using a 4.5-kg α-phase plutonium sphere surrounded with HEU was performed to demonstrate how well the computer transport code and the existing cross-section data for uranium and plutonium could reproduce the experiment. For some of the configurations, the prompt-neutron decay constants at delayed critical were measured. These experiments provided an integral measurement of the cross sections for 237Np in the fast-energy and possibly in the intermediate-energy regions. The measured keff from these experiments was compared with the calculated keff from the Monte Carlo N-Particle (MCNP) transport code using ENDF/B-V and ENDF/B-VI and cross-section data evaluated by the Nuclear Theory and Applications group (T-16) at LANL. In all the neptunium experiments, the calculated keff values based on ENDF/B-VI data were ~1% lower than the experimental keff. After adjusting the cross sections for neptunium and 235U to match the bare neptunium/HEU experiment as well as Godiva keff criticality and spectra indexes, the MCNP code yielded a value of 57 ± 4 kg for the bare critical mass of 237Np.

Cross Sections for Neutron-Induced Fission of 235U, 238U, 209Bi, and natPb in the Energy Range from 33 to 200 MeV Measured Relative to n-p Scattering

The cross sections for neutron-induced fission of 235U, 238U, 209Bi, and natPb in the intermediate-energy region were measured using parallel plate fission ionization chambers. The experiments were carried out relative to the differential n-p scattering cross section using quasi-monoenergetic neutron beams with peak energies ranging from 33 to 200 MeV. The experimental cross sections were compared to International Nuclear Data Committee reference fission cross sections, to results of nuclear model calculations, and to cross sections calculated with the nuclear models implemented in the radiation transport code MCNPX. The experimental results for 235U and 209Bi are consistent with the available reference cross sections and theoretical data while the 238U(n,f) cross section exceeds the reference cross section systematically by ˜7% between 30 and 60 MeV. The experimental results for natPb agree with a parameterization of other experimental data for natPb(n,f).

Precision measurements of the np scattering differential cross section in the intermediate energy region

In fast neutron cancer therapy, approximately 50% of the cell damage is caused by recoil protons from neutron-proton (np) scattering. In the intermediate energy region, there is a need for unambiguous np scattering data with good precision in both the shape of the angular distribution and the absolute normalisation. The normalisation techniques have been reviewed for np scattering measurements as well as recent experimental results, particularly the data obtained at The Svedberg Laboratory at 96 and 162 MeV. In addition, to what extent systematic uncertainties in the np differential cross section might affect the determination of proton recoil kerma coefficients is investigated.

Investigation of the reaction mechanism for the four-particle photodisintegration of a carbon nucleus

The four-particle photodisintegration of a carbon nucleus in the reactions 12C(γ, p)3H2α and 12C(γ, n)3H2α is investigated by a method that employs a diffusion chamber in a magnetic field. It is shown that these reactions proceed according a sequential-type scheme: excited states of 11B and 11C nuclei decay to weakly excited states of 8Be, 7Li, and 7Be nuclei. It is concluded that nucleons are knocked out from the s shell. In the excitation curve for the 2α system in the reaction 12C(γ, p)3H2α, a resonance is found between the maxima corresponding to the ground and the first excited state of the 8Be nucleus, and this resonance is identified as a ghost anomaly. The branching fractions of the decay modes are determined. The angular distributions of nucleons in the reaction c.m. frame are measured. The energy dependence of the asymmetry coefficient for the angular distributions is obtained. A fast increase in this coefficient is observed in the energy range 38–40 MeV. It is concluded that the asymmetry coefficient depends on the excitation energy of the final nucleus in the region of intermediate photon energies.

A study of photon interaction parameters in some commonly used solvents

Various parameters of dosimetric interest such as mass attenuation coefficients, effectiveatomic numbers and electron densities of some commonly used solvents such as acetonitrile(C4H3N),butanol (C4H9OH),chlorobenzene (C6H5Cl), diethylether (C4H10O), ethanol (C2H5OH), methanol (CH3OH), propanol (C3H7OH) and water (H2O) were computed in the wide energy range of 10 keV–100 GeV. A comparative studyof two different methods used to compute effective atomic numbers has beendone. It is observed that in the intermediate energy region (0.1–5 MeV), the massattenuation coefficient values becomes almost the same for all the solvents, andthe effective atomic number and electron density show almost constant values,whereas significant variation is observed in both lower (10–100 keV) and higher(5 MeV–100 GeV) energy regions for all the solvents, which may be due to thedominance of different partial interaction processes in different energy regions.

Coulomb oscillations in the electron thermal conductance of a dot in the linear regime

The electron thermal conductance, $\ensuremath{\kappa}$, of a dot has been calculated in the regime of weak coupling with two electrode leads within a linear response theory. We discuss the effect of the interplay between the charging energy, the thermal energy, and the confinement in the Coulomb oscillations of $\ensuremath{\kappa}$. Hence, we consider three energy regions: the quantum limit, where quantum confinement dominates over the thermal energy; the classical regime, where the discreteness of the energy spectrum is screened by the thermal energy; and the intermediate energy region. In the quantum limit, the periodicity of the oscillations of the electron thermal conductance is the same as the Coulomb-blockade oscillations of the conductance, $G$. Analytical expressions have been obtained for $\ensuremath{\kappa}$ and $G$ in the cases of nondegenerate and for doubly degenerate energy spectrum. The obtained dependence of $\ensuremath{\kappa}$ on the energy level spacing and the thermal energy explicitly shows that quantum confinement is responsible for the fast decrease of the electron thermal conductance of a dot. It is found that degeneracies in the energy spectrum of a dot are opposed to the decrease of the electron thermal conduction due to quantum confinement. It is shown that an external field that raises the degeneracies causes a considerable enhancement in $\ensuremath{\kappa}$. In the classical and in the intermediate regimes, the electron thermal conductance shows distinct behavior at low and high temperatures. In the classical regime, Coulomb blockade oscillations are shown at low temperatures and simple formulas are obtained for $\ensuremath{\kappa}$ and $G$. The Wiedermann-Franz law holds at the peaks of $\ensuremath{\kappa}$ and $G$. The temperature dependence of $\ensuremath{\kappa}$ and $G$ has been calculated up to the limit where transport occurs through two isolated barriers. The relation between $\ensuremath{\kappa}$ and $G$ with increasing thermal energy is discussed.

A study of the cross sections and the spin observables for proton-12C elastic scattering in momentum space in the intermediate energy region

The differential cross sections and the spin observables of p-12C elastic scattering in the whole intermediate energy region are calculated using the KMT multiple scattering theory with microscopic momentum space optical potential which incorporates the spin dependence of the NN and p-12C interactions. The theory takes into consideration the antisymmetrized NN amplitudes, nucleon recoil and binding energy shifts, Lorentz invariant angle transformations, t matrices with on-shell behavior from NN phase shifts,and off-shell behavior from a realistic separable potential model. Qualitative agreement is found in differential cross sections and polarization data for 200Ep<1000 MeV.

GENETIC PROGRAMMING APPROACH FOR ELECTRON-ALKALI-METAL ATOM COLLISIONS

New technique is presented for modeling the total cross sections of electron scattering by Na, K, Rb and Cs atoms in the low and intermediate energy regions. The calculations have been performed in the framework of genetic programming (GP) technique. The GP has been running based on the experimental data of the total collisional cross sections to produce the total cross sections for each target atom. The incident energy and atomic number as well as the static dipole polarizability have been used as input variables to find the functions that describe the total collisional cross sections of the scattering of electrons by alkali atoms. The experimental, calculated and predicted total collisional cross sections are compared. The discovered functions show a good match to the experimental data.

Determination of the full response function of personal neutron dosemeters

The response of neutron dosemeters may be determined directly from measurements, provided a sufficiently large number of measurements in monoenergetic neutron fields covering the entire energy range of interest is available. In practice this is not feasible due to the lack of monoenergetic neutron fields in the thermal and intermediate energy region (i.e. energies<24 keV). To deal with this difficulty, we have developed a method which can take into account additional information about the response of the dosemeter. Our analysis makes use of two types of data, measurements made using monoenergetic neutron beams and measurements made in neutron fields with broad energy distributions. The dosemeter responses are described using a parametrised model, based on a minimum of assumptions: that they should fit the data within experimental uncertainties, and that they should remain close to a simple interpolation of the monoenergetic and thermal neutron field data.

Weak quasielastic production of hyperons

The quasielastic weak production of $\ensuremath{\Lambda}$ and $\ensuremath{\Sigma}$ hyperons from nucleons and nuclei induced by antineutrinos is studied in the energy region of some ongoing neutrino oscillation experiments in the intermediate energy region. The hyperon-nucleon transition form factors determined from neutrino-nucleon scattering and an analysis of high precision data on semileptonic decays of neutron and hyperons using SU(3) symmetry have been used. The nuclear effects due to Fermi motion and final state interaction effects due to hyperon-nucleon scattering have also been studied. The numerical results for differential and total cross sections have been presented.

Nuclear Effects in Neutrino Induced Coherent Pion Production at K2K and MiniBooNE

The coherent pion production induced by neutrinos in nuclei is studied using a delta hole model in the local density approximation taking into account the renormalization of Delta properties in a nuclear medium. The pion absorption effects are included in an eikonal approximation. These effects give a large reduction in the total cross section. The numerical results for the total cross section are found to be consistent with recent experimental results from the K2K and MiniBooNE Collaborations and other older experiments in the intermediate energy region.