Total Cross Research Articles

Experimental check of the GDH sum rule at MAMI and ELSA

An extensive experimental program was carried out at MAMI (Mainz) and ELSA (Bonn) to measure pion photo-production reactions on the nucleon in double polarization and to investigate the Gerasimov-Drell-Hearn Sum Rule. We obtained results for the proton in the energy range from about 200 MeV to 3000 MeV and for the neutron, using a deuteron target, from about 200 MeV to 1900 MeV. Preliminary results on the total absorption cross sections are presented and discussed.

Total Reaction Cross Sections of11C on Plastic Scintillator in the Energy Range of 100–345 MeV/u

This article gives a new experimental estimate of the fraction of 11 C nuclear absorption in plastic scintillator, (C 9 H 10 ) n , according to nuclear reactions, and compares the results with an empirical formula based on a microscopic nuclear reaction model by Kox et al. [Phys. Rev. C 35 (1987) 1678]. The result establishes that the model is applicable to 11 C.

Observation of large rapidity gap events in charged current deep inelastic scattering at HERA

Events with a large rapidity gap have been observed in e + p charged current DIS at HERA. The data collected with the ZEUS detector in the running period 1999 and 2000 correspond to an integrated luminosity of 61 pb −1 . The excess in the yield of such events over the non-diffractive DIS expectation has been compared to models of diffractive scattering in the electroweak regime. The diffractive charged current cross section for the kinematic range Q 2 > 200 GeV 2 and x P 0.05 as well as its ratio to the total charged current cross section have been calculated.

Probing s-Channel Unitarity With LRG Signatures

Hard diffractive di-jets with large rapidity gap (LRG) signatures are explored following the Tevatron and HERA observations that their production rates are considerably smaller than the pQCD estimates. It is argued that a consistent description of these data can be attained only after s -channel unitarity re-scattering screening corrections are incorporated. To this end a simple and very successful procedure is presented in which information derived from the measured soft total, elastic and diffractive cross sections simplifies the calculation and makes it parameter free. Consequently, we consider LRG hard diffraction an excellent probe to explore the role of s -channel unitarity in high energy soft scattering.

Total cross sections for electron scattering at 10–5000 eV by polyatomic molecules CF 4, CF 3 H, C 2 F 4 , C 2 F 6 and C 2 H 3 F 3

The additivity rule and complex optical potential approach have been employed to obtain the total (elastic and absorption) cross sections for electron scattering by molecules (CF4, CF3H, C2F4, C2F6 and C2H3F3) over an incident energy range from 10 to 5000 eV. Compared with other calculations and experimental data wherever available, excellent agreement has been obtained. Above 1000eV, there are no experimental data for CF3H, C2F4, C2F6 and C2H3F3, so the present results can provide comparison and predictions for experimental research.

Total and single differential cross sections for simple resonant collisions using a fully orthonormal continuum-distorted-wave basis

Simple electron capture processes are studied using an orthonormal two state continuum-distorted-wave (CDW) basis. The suitability of the basis set is tested by comparing predictions for total and differential cross sections with available experimental data. Overall good agreement is obtained and the authors conclude that a relatively small CDW basis set may be suitable to model a wide variety of low-energy collisions if the members of this extended set are astutely chosen.

ANALYSIS OF HIGH ENERGY K+K- PHOTOPRODUCTION ON HYDROGEN

We have analyzed the γp→pK+K- reaction in the K+K- effective mass region around the mass of the ϕ(1020) meson. The interference of the S-wave contribution with the P-wave has been studied. Both scalar resonances f0(980) and a0(980) have been taken into account. We obtained a good description of the available experimental data, in particular the mass distributions and the moments of the kaon angular distribution. Our calculations give values of the integrated S-wave total photoproduction cross section between 4 and 7 nb for the K+K- effective mass range around the ϕ(1020) mass and at the laboratory photon energy near 5 GeV. These numbers favor lower experimental estimates obtained at DESY.

Iterative Approach to Scattering from the Targets above a Rough Surface

The difference field RCS from a target above a rough surface is derived. The electric field integral equations (EFIE) of the difference induced currents Jsd on the surface and J0 on target are developed. Because of the strongest scattering in the specular direction, a small interface taken along the converse specular direction is attributed to computation of the surface scattering upon the target. A fast mutual-coupling iterative method is developed to solve the two EFIEs. The interface length for effective computation is discussed. Using the Monte Carlo method, scattering from a target, such as a cylinder and a square column, above the P-M rough surface is numerically simulated. Scattering from a cylinder above the rough surface in the specular direction is enhanced significantly. The Bi-RCS of a square column above the rough surface shows two peaks in forward and backward directions. As a model of rough sea surface, when the surface wind speed increases, the scattering peaks become lower, and more defused scattering shows the angular scattering pattern. Introduction Scattering from the targets above a rough surface has attracted more interests in recent years. In the combined target-surface problem, the difference field cross section was introduced by Johnson [1] to remove the dependence on incident taper wave width. Scattering for the combined target-surface problem and surfaceonly problem are respectively calculated, and their difference shows scattering attributed by the target and interaction between the target and rough surface. In this paper, we derive the EFIEs of the difference induced current on rough surface and current on the target. A mutual-coupling iterative approach is developed to solve the EFIEs. The interface length for the iterative calculation is discussed. As examples, scattering from a cylinder and a square column above a rough surface are simulated. It can be seen that scattering from the cylinder above a rough surface is significantly enhanced in the specular direction due to interactions of the target and the underlying surface. Variation of the difference induced currents on the interface also demonstrates such interactions. Scattering from a square column has two peaks in the backward and forward directions due to its specific geometry. As a model of a target located above the wind-driven sea surface, numerical simulations show the angular pattern of bistatic scattering versus oceanic status. When the surface wind speed increases, scattering peaks become weaker and more angular defused scattering are dominated. Theory and Method In a model of the target above rough surface, both the total and differential cross section are previously related to the surface length illuminated by incident wave. In order to remote the dependence on illuminated surface length, the difference of the scattering field, Es1, attributed by both the target and surface and the scattering field by a rough surface only, Es0, is calculated as Esd, which is used to compute the difference field cross section σd [1], which demonstrates how much the scattering attributed by the target and interaction between the target and underlying rough surface. It does not depend upon the illuminated rough surface length. As shown in Fig.1, a two-dimensional (2D) target (perfect electric conductor, PEC) is located above a 2D PEC rough surface. As the incident tapered wave is incident on the target and rough surface, the induced current on the target is defined as J0, and the induced current on the surface is Js1. The EFIEs are written as [2] 0 = ET (r)− jkη ∫ c Jo(r ′) ·G(r, r′)dr′ − jkη ∫ S Js1(r ′) ·G(r, r′)dr′(r ∈ c) (1) 202 Progress In Electromagnetics Research Symposium 2005, Hangzhou, China, August 22-26

Experimental upper limit on diffractive dissociation in muon-neutrino interaction with photoemulsion nuclei according to data of the E-128 experiment (Protvino)

The phenomenon of diffractive dissociation is experimentally estimated for neutrino interaction with photoemulsion nuclei. The results are based on data obtained in the SCIP experiment performed in a neutrino beam at the U-70 accelerator (Protvino). The data sample subjected to analysis included 670 charged-current events corresponding to neutrino interactions in the vertex detector. Events in which the Bjorken variable was x=0–0.1 were selected from this sample. Upon going over to the variable x′, which takes into account the nucleon mass, we set an upper limit of 0.53±0.07 on the diffractive-dissociation contribution to the total charged-current cross section.

Total electron scattering cross sections ofKrandXein the energy range250–4500eV

Total electron scattering cross sections are reported for $\mathrm{Kr}$ and $\mathrm{Xe}$ for $250--4500\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ electrons by measurement of the electron-beam intensity attenuation through a gas cell. These cross sections are compared with the previous experimental measurements and the predictions by theoretical and semiempirical models. Discrepancies in experimental cross sections between different experimental groups are explained using the oscillator strengths and inelastic threshold of electron-energy-loss spectra. The correlation between the total electron scattering cross section and the atomic radius is discussed for $\mathrm{Ne}$, $\mathrm{Ar}$, $\mathrm{Kr}$, and $\mathrm{Xe}$ atoms.

Elastic electron scattering from Ba and Sr

We present a comprehensive set of theoretical results for differential, total, and momentum transfer cross sections and Sherman functions for the elastic scattering of electrons by barium and strontium atoms, for the entire angular range and energies below 1 keV. This study extends our method of calculations, already employed for inert gases, to other atoms with closed subshells and provides insight into the electron scattering from these two atoms, particularly for strontium where there is a serious lack of both experimental and prior theoretical works. Our relatively simple semiempirical approach, with a single adjustable parameter, produces a satisfactory agreement with the measured values and convergent close-coupling calculations for barium, for the limited number of energies and angles at which they are available. Based on this success, we provide a recommended set of values of cross sections and scattering phase shifts for both atoms and for future applications.

Nuclear Data Evaluations on Zirconium, Niobium and Tungsten for Neutron and Proton Incidence up to 200 MeV

Nuclear data were evaluated on 90 91 92 94 96Zr, 93Nb and 182 183 184 186W for neutron and proton incidence up to 200 MeV. Optical model potential parameters were searched to give good agreements with experimental values of elastic-scattering, total, and total-reaction cross sections. The GNASH pre-equilibrium/statistical model code was used for evaluations of particle-production cross sections. Since the direct inelastic-scatterings induced by the excitations of giant resonances are not negligible for these nuclei, the calculation was performed to take them into consideration. For composite-particle emission cross sections from pre-equilibrium states, semi-empirical methods were utilized to give good agreements with experimental results. We also calculated isotope-production cross sections. Evaluated cross sections were compared with values by measurements and the LA150 evaluations.

R-matrix calculations of the integral electron-impact excitation cross sections of the ground state of the barium atom

The R-matrix approach has been used to calculate the integral cross sections of excitation of the barium atom by low-energy electrons. The collision strengths have been calculated in the 38-state close coupling approximation, including 16 physical states and 22 pseudostates of the target. The target wave functions have been obtained in terms of the multiconfiguration Hartree-Fock method in the LS coupling scheme. The cross sections calculated exhibit a pronounced resonance structure, which contributes significantly to the total excitation cross sections. The results obtained have been compared to available theoretical and experimental data.

Calculating Probability Tables for the Unresolved-Resonance Region Using Monte Carlo Methods

A new module, Probability tables for the Unresolved Region using Monte Carlo (PURM), has been developed for the AMPX-2000 cross-section–processing system. PURM uses a Monte Carlo approach to calculate probability tables on an evaluator-defined energy grid in the unresolved-resonance region. For each probability table, PURM samples a Wigner spacing distribution for pairs of resonances surrounding the reference energy (i.e., energy specified in the cross-section evaluation). The resonance distribution is sampled for each spin sequence (i.e., l-J pair), and PURM uses the Δ3-statistics test to determine the number of resonances to sample for each spin sequence. For each resonance, PURM samples the resonance widths from a chi-square distribution for a specified number of degrees of freedom. Once the resonance parameters are sampled, PURM calculates the total, capture, fission, and scatter cross sections at the reference energy using the single-level Breit-Wigner formalism with appropriate treatment for temperature effects. Probability tables have been calculated and compared with NJOY. The probability tables and cross-section values that are calculated by PURM and NJOY are in agreement, and the verification studies with NJOY establish the computational capability for generating probability tables using the new AMPX module PURM.

Ionization ofArby energetic proton impact

Available theoretical total and differential cross sections for the ionization of argon atoms by energetic proton impact are discussed and compared with our present calculations. The results depend sensitively on the model potential used for the description of the unperturbed atomic orbitals. Remarkable post-prior discrepancies are found when the electron-target interactions are calculated with respect to different potentials for the initial and final channels, respectively. Not only the orthogonality between bound and continuum wave functions, but also the correct asymptotic behavior of the exchange part of the potential is crucial for a satisfactory description of the experimental data.

Cross sections of electron inelastic interactions in DNA

The cross sections of electron inelastic interaction in DNA are calculated using the dielectric response theory and Penn statistical approximation, with the exchange correction included. An empirical approach to obtain optical energy loss function is given for the organic compounds without available optical data. Comparisons of the calculated data with available experimental and theoretical results have been done to show the reliability of the approach proposed in this work. Using this approach, the total inelastic cross sections for five bases: guanine, adenine, thymine, cytosine and uracil have been calculated in the energy range of E< or =10 keV and compared with those recently obtained with the Deutsch-Mark formalism and the Binary-Encounter-Bethe model, respectively. An equivalent unit of the DNA molecule is constructed according to the contents of A-T and G-C base pairs in DNA, and is divided into five constituents, i.e. sugar-phosphate and four bases. The total inelastic cross sections for the constructed unit of the DNA molecule and its constituents have also been calculated.

Production of heavy nuclei in the interaction of 7Li ions with copper nuclei at an energy of 35 MeV per nucleon

The absolute values of the cross sections for the production of target fragments in the interaction of copper with 7Li ions at an energy of 35 MeV per nucleon were measured. The measurements were performed by recording the yields of radioactive nuclear residues with the aid of a semiconductor detector from ultrapure germanium. The charge and isobaric distributions in the mass-number range 22–69 amu were used to deduce the mass yield of reaction products and to calculate the total interaction cross section. The results are presented that were derived from a comparison with data obtained for 12C + Cu reactions and with estimates based on theoretical models.

Photofission of actinide nuclei in the nucleon-resonance region: First photonuclear experiment at the Siberia-2 storage ring

Results of an experiment performed to study 238U photofission with the aid of the initial section of the GAMMA channel of the Siberia-2 storage ring at the Kurchatov Institute are presented. These results are predominantly of a methodological value, because a photonuclear experiment was conducted for the first time in this channel. However, the data obtained in this way allowed us to evaluate an upper limit on the probability of the fast fission (fragmentation) of 238U nuclei that was induced by photons of energy up to 2.5 GeV. This is pertinent to the problem of the deviations of the total photoabsorption cross sections for actinide nuclei from a “universal curve.”

Photodisintegration of Light Nuclei

The first microscopic calculation of inelastic reactions on nuclei with mass number A = 6 is presented. In particular, we consider the total photoabsorption cross section of 6He and 6Li. It is shown that the halo nucleus 6He exhibits two types of dipole resonances, the normal giant dipole resonance and a low-energy soft dipole resonance associated with the excitation of the outer neutrons. Comparing our results with available experimental data we note the role of P-wave interaction. Calculations are performed using the Lorentz integral transform (LIT) method and the effective interaction in the hyperspherical harmonics formalism (EIHH).

243. Delivery of Igf-I and Dystrophin to Dystrophic mdx Muscle

Duchenne muscular dystrophy is among the most common genetic diseases and is caused by mutations in the dystrophin gene. Dystrophic muscles display an extensive degeneration and regeneration process, whereby muscle fibers progressively lose their self-renewal potential and are gradually replaced by adipose and fibrotic tissue. Gene replacement therapy using truncated versions of dystrophin have been shown to protect dystrophic muscles from contraction-induced injury and partially reverse muscle pathology. An alternative approach involves the activation of satellite cells to maintain the regenerative potential of dystrophic muscle. Igf-I, an important mediator of cell growth and differentiation, has been shown to increase muscle mass and strength and to enhance muscle repair mechanism in dystrophic mdx muscles (Barton et al., 2002). However, Igf-1 is unable to restore mechanical integrity to muscle fibers lacking dystrophin. To determine if the beneficial effect of Igf-I is synergistic with the protective effect of dystrophin in ameliorating dystrophic pathology, we compared the effects of delivering Igf-I alone versus co-delivering both Igf-I and dystrophin to adult, dystrophic mdx mouse muscles. We generated recombinant adeno-associated viral vectors pseudotyped with the serotype 6 capsid protein that carry expression cassettes in which the muscle-specific creatine kinase promoter/enhancer drove either the micro-dystrophin (AAV-udys) or the Igf-I cDNA (AAV-Igf-I). Tibialis anterior muscles of mdx mice were injected with each vector separately, together or with buffer control and then analyzed four months post injection. Immunohistochemical analysis demonstrated persistent expression of dystrophin that reached an average of 40% of the total muscle cross sectional area. We also observed persistent expression of Igf-I mRNA at levels 200-400 fold greater than endogenous mdx Igf-I levels in AAV-Igf-I and AAV-udys co-injected muscles. In contrast, injection of AAV-Igf-I alone resulted in a 4-fold decline of Igf-I mRNA levels in the four months following injection into dystrophic mdx muscles. Functional measurements demonstrated that AAV-udys injected animals were partially protected from contraction-induced injury after two lengthening contractions, whereas animals injected with AAV-Igf-I alone were as susceptible as mdx animals to muscle damage. AAV-Igf-I treated animals, on the other hand, showed an increase in muscle mass, which was not seen after AAV-udys only treatment. In contrast, co-injection of AAV-Igf-I and AAV-udys resulted in increased muscle mass and muscle strength, and in protection from contraction-induced injury. These results suggest that the combination of AAV-Igf-I and AAV-udys acted synergistically and was beneficial for the animal.