Measurements Of Elastic Scattering Cross Sections Research Articles

Radiative corrections beyond the ultra relativistic limit in unpolarized ep elastic and Møller scatterings for the PRad Experiment at Jefferson Laboratory

The clear 7σ discrepancy between measurements of the proton charge radius from muonic hydrogen Lamb shifts and those from hydrogen Lamb shift and electron scattering lead to both intense theoretical and experimental efforts to understand and explain this difference. In this regard, a new experiment (PRad) based on unpolarized ep elastic scattering cross section measurements normalized to Møller scattering is underway at Jefferson Laboratory to extract the proton charge radius based on new proton electric form factor down to values of momentum transfer squared Q 2, as low as 10−4 GeV/c)2. To reach the precision of the experiment in such a small Q 2 region requires reliable knowledge of radiative corrections. In this paper, we present a complete calculation of radiative corrections for unpolarized elastic ep and Møller scatterings performed within a covariant formalism resulting in the set of explicit formulas beyond the ultra relativistic approximation (m 2 ≪ Q 2), and numerical results for the kinematics of the PRad experiment.

Reprint of: Neon interatomic potentials from scattering data and crystalline properties

Interatomic potentials for Ne2 derived from recent differential elastic scattering cross section measurements and properties of solid neon are presented. Cross sections and second virial coefficients are calculated with the proposed potentials and comparisons with experiment are made. The Ne2 potential derived from scattering data only is shown to provide a good fit to the solid state data.

Neutron Elastic Scattering Cross-Section Measurements at 175 MeV

An off-line data analysis of an experimental campaign on elastic neutron cross-section measurements at 175 MeV for iron and bismuth performed by the SCANDAL set-up has started. Energy calibration has shown expected values of energy resolution and MCNPX simulations have provided suggestions for further analysis.

Coupling between positronium formation and elastic positron-scattering channels in the rare gases

Measurements of elastic-scattering cross sections are presented for positron collisions with helium, neon, argon, krypton, and xenon around the threshold energy for positronium (Ps) formation. The elastic cross section falls slowly with increasing energy above the Ps formation threshold in helium and neon, whereas in argon, krypton, and xenon it exhibits an increase, which appears both more prominent and more sustained as the atomic number of the gas increases. It is proposed that this coupling is a result of an intermediate virtual Ps state that enhances branching into the (atom plus positron) final state.

Quantum mechanical scattering cross sections and permeability coefficients for ions crossing the human red cell and resting squid axon membranes

Quantum mechanical calculations of elastic scattering cross sections for some permeant ions crossing the human red blood cell and resting axolemma squid axon membranes have been carried out using the three-dimensional spherically symmetric square potential well. Making the assumption that the permeability coefficient is inversely proportional to scattering cross section, we obtain the order of membrane selectivity for the ions as well as values for the permeability coefficients. Despite the relatively simple method used, good agreement between calculated permeability coefficients and data available in the literature is obtained. We suggest that elastic scattering cross section measurements for ions in various membranes would be valuable not only because they give a precise idea about the permeability ratios between ions but they also determine the form of the potential the ions are moving in.

Electric isovector nuclear response from 13C induced charge-exchange reactions

The reaction ( 13C, 13N) has been studied at 50 MeV/u on a set of nuclear targets including 12C, 40Ca, 58,60Ni, 90Zr, 120Sn and 208Pb. Excitation of ΔT 2 = 1 giant dipole resonance has been observed in light nuclei ( A⩽ 60) and corresponding angular distribution have been measured. A broad structure is observed at excitation energy above the GDR in nuclei with A⩾ 60. Angular-distribution measurements of elastic-scattering cross sections are also reported on 12C and 58Ni, as well as excitation of low-lying states in 12B. Microscopic DWBA analysis of the results is presented. Some results on the ( 13C, 13B) reaction are also presented.

14N+ 10B fusion and elastic scattering cross section measurements near the interaction barrier

The 14N+ 10B fusion reactions were studied at c.m. energies between 2.9 and 7.5 MeV by measuring the yields of γ-rays from the residual nuclei formed by particle evaporation from the compound system. Cross sections for formation of the evaporation residues 16O, 19F, 19Ne, 20Ne, 21Ne, 22Ne, 22Na, 23Na and 23Mg, as well as the total cross section, were deduced from these yields with the aid of statistical model calculations. The 14N+ 10B elastic scattering differential cross sections were measured from E c.m. = 4.3 to 9.1 MeV at θ c.m. = 74.4°, and from E c.m. = 3.3 to 8.3 MeV at θ c.m. = 90.0°. The elastic scattering cross sections were analyzed within the framework of the incoming-wave boundary condition (IWBC) model. The fusion cross sections calculated for the real ion-ion potential deduced from the IWBC model fit to the elastic scattering are in good agreement with the measured values.

Neutron elastic scattering cross section measurements at back angles

The optical model has frequently been used to give a theoretical description of experimental neutron elastic scattering angular distributions. In such experiments the differential cross sections should be studied in as large an angular interval as possible. However, hitherto the published results have mostly been confined to the angular region 20° to 160°. The extension of the studied angular range to extreme backward angles is of theoretical interest since this would provide an opportunity for studying the influence of the depth of the spin-orbit term of the optical-model potential on the shape of the angular distribution in greater detail. This is possible because of the high sensitivity of the calculated differential elastic scattering cross sections at backward angles to the depth of the spin-orbit term. Thus in this paper an experimental arrangement is described which allows measurements at extreme backward angles. With this arrangement measurements have been performed at angles up to 174° for Fe, Co, In and Bi at a primary neutron energy of 7.05 MeV. It has been found that the observed differential cross sections for Fe and Co are best described by those calculated with the depth of the spinorbit term equal to 6 MeV while a value of 4 MeV may be a better choice for In and Bi.

ArHCl interaction potential from differential elastic scattering cross section measurements

The crossed molecular beam technique has been used to determine the ArHCl spherically symmetric potential. Analysis of the data obtained at a relative collision energy of 12.4 × 10 −14 erg (1.78 kcal mole −1) yields a potential with ϵ/ k = 191°K, r m = 4.0 Å. These results are shown to be in agreement with other experimental conclusions on the ArHCl van der Waals complex as well as with transport phenomena.

Neon interatomic potentials from scattering data and crystalline properties

Interatomic potentials for Ne 2 derived from recent differential elastic scattering cross section measurements and properties of solid neon are pres Cross sections and second virial coefficients are calculated with the proposed potentials and comparisons with experiment are made. The Ne 2 potential derived from scattering data only is shown to provide a good fit to the solid state data.

Interaction Energies from Scattering Cross Sections of Hydrogen Ions in CH4, CF4, C2H6, and C2F6

The potential energy curves for the interactions between hydrogen ions (H+, H2+) and CH4, C2H6, CF4, and C2F6 have been determined from the elastic scattering cross section measurements of Simons and co-workers. The scattering measurements indicate no minimum in the H+–CH4 potential curve as one might expect from the fact that mass spectrographic results indicate a proton affinity of 5 ev for CH4. Reasons are suggested why no minimum is indicated. Various crude semiempirical schemes are suggested for correlating the potential curves for the different interaction systems. All suggested schemes are tested on the experimental results and are found to reproduce the measured potentials to within a factor of 2.