F. S. Dietrich

Measurements of the Proton and Deuteron Spin Structure Function g2 and Asymmetry A2

We have measured proton and deuteron virtual photon-nucleon asymmetries A2p and A2d and structure functions g2p and g2d over the range 0.03<x<0.8 and 1.3<Q2<10 (GeV/c)2 by inelastically scattering polarized electrons off polarized ammonia targets. Results for A2 are significantly smaller than the positivity limit sqrt(R) for both targets. Within experimental precision, the g2 data are well-described by the twist-2 contribution g2WW. Twist-3 matrix elements have been extracted and are compared to theorectical predictions.

Measurements of R = σL/σT for 0.03 < x < 0.1 and Fit to World Data

Abstract Measurements were made at SLAC of the cross section for scattering 29 GeV electrons from carbon at a laboratory angle of 4.5°, corresponding to 0.03Measurements were made at SLAC of the cross section for scattering 29 GeV electrons from carbon at a laboratory angle of 4.5 degrees, corresponding to 0.03<x<0.1 and 1.3<Q^2<2.7 GeV^2. Values of R=sigma_L/sigma_T were extracted in this kinematic range by comparing these data to cross sections measured at a higher beam energy by the NMC collaboration. The results are in reasonable agreement with pQCD calculations and with extrapolations of the R1990 parameterization of previous data. A new fit is made including these data and other recent results.

Microscopic and conventional optical model analysis of neutron elastic scattering at 21.6 MeV over a wide mass range

Abstract Differential fast neutron elastic scattering angular distributions have been measured at 21.6 MeV for the natural elements Mg, Al, Si, S, Ca, Cr, Fe, Co, Ni, Y, Ce, Pb r (radiogenic lead) and Bi by employing pulsed beam time-of-flight techniques. The energy resolution was about 0.5 MeV (FWHM) throughout the measurements. The experimental data have been analysed in terms of a standard phenomenological spherical optical model. Potential depths and geometrical parameters were determined from individual best fits to the data. Volume integrals of the real and imaginary parts of the potential were calculated using these parameters. A similar technique was utilized to calculate root mean square radii of the real potential, from which radii of point matter distributions were obtained for comparison with α-particle scattering data at 166 MeV and with charge distribution radii from electron scattering. Microscopic folding models for the optical potential according to Jeukenne, Lejeune and Mahaux, Brieva and Rook, and Yamaguchi et al . have been tested by calculating angular distributions, volume integrals and root mean square radii for the real and imaginary potential parts. The results of these calculations are compared with those of the phenomenological analyses. The microscopic potentials have also been intercompared by studying introduced normalizing parameters of the real and imaginary potential parts as well as isovector and isoscalar contributions to the volume integrals.

Consistent folding model description of nucleon elastic, inelastic, and charge-exchange scattering from 6,7Li at 25–50 MeV

Abstract The results of a consistent theoretical microscopic single scattering model study of nucleon elastic, inelastic, and charge-exchange scattering from 6,7 Li at E p(n) = 25–50 MeV are reported. A realistic effective nucleon-nucleon interaction, adopted from the work of Mahaux and collaborators and Bertsch and coworkers, has been employed in the model calculations. The density distributions needed to describe the structure of the mass 6 and 7 systems in the calculations are the same as those used in recent proton-nucleus scattering studies of these targets at E p = 200 MeV. The present, parameter-free model calculations provide an excellent description of the available low-energy nucleon-nucleus scattering data on 6,7 Li.

Measurements of the Delta(1232) transition form factor and the ratio sigma(n)/sigma(p) from inelastic electron-proton and electron-deuteron scattering

Measurements of inclusive electron-scattering cross sections using hydrogen and deuterium targets in the region of the Delta(1232) resonance are reported. A global fit to these new data and previous data in the resonance region is also reported for the proton. Transition form factors have been extracted from the proton cross sections for this experiment over the four-momentum transfer squared range 1.64 < Q~2 < 6.75 (GeV/c)~2 and from previous data over the range 2.41 < Q~2 < 9.82 (GeV/c)~2. The results confirm previous reports that the Delta(1232) transition form factor decreases more rapidly with Q~2 than expected from perturbative QCD. The ratio of sigma _n \sigma_p in the \Delta(1232) resonance region has been extracted from the deuteron data for this experiment in the range 1.64 < Q~2 < 3.75 (GeV/c)~2 and for a previous experiment in the range 2.4 < Q~2 < 7.9 (GeV/c)~2. A study has been made of the model dependence of these results. This ratio sigma_n\sigma_p for \Delta(1232) production is slightly less than unity, while sigma_n\sigma_p for the nonresonant cross sections is approximately 0.5, which is consistent with deep inelastic scattering results.

Determining neutron capture cross sections via the surrogate reaction technique

Indirect methods play an important role in the determination of nuclear reaction cross sections that are hard to measure directly. In this paper we investigate the feasibility of using the so-called surrogate method to extract neutron capture cross sections for low-energy compound-nuclear reactions in spherical and near-spherical nuclei. We present the surrogate method and develop a statistical nuclear reaction simulation to explore different approaches to utilizing surrogate reaction data. We assess the success of each approach by comparing the extracted cross sections with a predetermined benchmark. In particular, we employ regional systematics of nuclear properties in the

Measurement of the proton elastic form factors for Q2=1−3(Gev/c)2☆

34\ensuremath{\leqslant}Z\ensuremath{\leqslant}46

Anomalous behavior of the n + 208Pb potential near the fermi energy☆

region to calculate

Toward a microscopic reaction description based on energy-density-functional structure models

(n,\ensuremath{\gamma})

A New Method for Estimating Neutron Reaction Cross Sections Based on Wick’s Limit

cross sections for a series of Zr isotopes and to simulate a surrogate experiment and the extraction of the desired cross section. We identify one particular approach that may provide very useful estimates of the cross section, and we discuss some of the limitations of the method. General recommendations for future (surrogate) experiments are also given.