Integral cross sections for the scattering of pions by protons into angles greater than 30 degrees (lab) have been measured at a wide range of energies spanning the delta resonance using liquid hydrogen targets. Cross sections were measured for nip scattering at 40 energies from 39.8 to 283.9 MeV and for pi(-)p at 15 energies from 80.0 to 283.9 MeV. Comparisons with phase shift predictions from the Karlsruhe group show good agreement on resonance but significant deviations below 100 MeV. [S0556-2813(99)02903-9].

Differential cross sections for pi(+) + C-12 elastic scattering in the energy range of 18-44 MeV for six scattering angles have been measured with an increment in the incident energy of 2 MeV. The measured cross sections are compared to calculations within the framework of a unitary scattering theory of the pion-nucleus interaction. It is shown that the excitation function at angles around 90 degrees is dominated by the D wave of the pion-nucleus interaction. [S0556-2813(98)05605-2].

In this paper we present the gross-count material basis set (GC-MBS) method for estimating transmission losses in measurements of radionuclides using low-resolution gamma-ray detectors such as NaI or CdZnTe. The application to continuum-subtracted peaks measured with high-purity Ge detectors is also discussed. To illustrate the method, we apply it to the correction of spectra from enriched uranium that have been distorted by various intervening absorbers. We also examine the application to simultaneous determination of the uranium enrichment through an unknown absorber using an NaI detector.

This work investigates the use of annihilation photons from gamma-ray-induced electron-positron pair production to inspect objects when only one side is accessible. The Z2-dependence of the pair-production cross section and the high penetration of 511-keV photons allow this method to differentiate high-Z materials in low-Z matrices. The experimental results for the dependence of the back-streaming photon yield on Z shows a factor of 20 increase for elements over the range 4<Z<82. Results for point-by-point “images” obtained in line scans of representative geometries are also shown. Comparisons of experimental data and simulation studies based on the EGS4 Monte Carlo code agree to within 5%

Pion-nucleus elastic scattering at energies above the Delta(1232) resonance is studied using both pi+ and pi- beams on 12C, 40Ca, 90Zr, and 208Pb. The present data provide an opportunity to study the interaction of pions with nuclei at energies where second-order corrections to impulse approximation calculations should be small. The results are compared with other data sets at similar energies, and with four different first-order impulse approximation calculations. Significant disagreement exists between the calculations and the data from this experiment.

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The collection of ions created by alpha particles in air is a powerful technique for detecting the presence of alpha-emitting radioactive contamination. These ions have a relatively long lifetime (greater than 5 seconds) in air so the ions can travel much longer distances than the alpha particles themselves. However, such ion detection is difficult when the object being surveyed is an insulating material. An insulating object does not release ions generated until the surface of the object has completely discharged. Thus, there are significant response-time problems with contamination on insulating objects. This project sought to investigate the technique of {open_quotes}flooding{close_quotes} the suspect object with ions prior to the actual contamination detection measurement. Our preliminary conclusion is that such flooding will enhance detection speed on insulating objects.

Measurements are presented for several mixtures of the spin observables C-SS, C-SL = C-LS, C-LL, and C-NN for neutron-proton elastic scattering. These data were obtained with a free polarized neutron beam, a polarized proton target, and a large magnetic spectrometer for the outgoing proton. The neutron beam kinetic energies were 484, 567, 634, 720, and 788 MeV Combining these results with earlier measurements allows the determination of the pure spin observables C-SS, C-LS, and C-LL at 384, 634, and 788 MeV for c.m. angles 25 degrees less than or equal to theta(c.m.)less than or equal to 180 degrees and at 720 MeV for 35 degrees less than or equal to theta(c.m.)less than or equal to 80 degrees. These data make a significant contribution to the knowledge of the isospin-0 nucleon-nucleon scattering amplitudes.

Studies of the production of the Delta resonance in hadronic charge exchange reactions show a shift in the Delta peak position. Measurements looking also at the Delta decay products give some evidence for coherent pion production. We have recently completed a new measurement of the C-12(p,n) reaction leading to the Delta resonance, including a higher resolution coincidence measurement of decay pi's in the forward direction. We describe the experiment and some aspects of the preliminary analysis.

Measurements of small-angle cross sections for the pion double-charge-exchange (DCX) reaction O-16(pi+,pi-)Ne-16(g.s.) at incident energies of 300-500 MeV are reported. These are the first measurements of DCX cross sections on a T = 0 nucleus in this energy region. The behavior of the cross sections is similar to that of analog transitions, but they are smaller by more than an order of magnitude. This suggests sequential charge-exchange scattering as the dominant process, but suppressed by a mechanism not yet identified.

Double charge exchange cross sections for 50 MeV pions to double isobaric analog states in Ca-44, Fe-56, and Nb-93 were measured. The results indicate that the effective double charge exchange operator at this energy has a strong short-range component. In addition, evidence is presented tending to implicate isospin mixing as the mechanism for excitation of the analog of the antianalog in Nb-93.

The search for an eta bound state in the double charge exchange (DCX) reaction to the double isobaric analog state (DIAS) 180(pi+,pi-)Ne-18(DIAS) has been carried out at LAMPF using the P3 channel and the LAS spectrometer. An excitation function for this reaction was measured for energies ranging from 350 to 440 MeV and for momentum transfers of 0, 105, and 210 MeV/c. The measured cross sections tend to agree with previous results for DCX on 0-18. The measured excitation function shows some evidence for structure near the eta production threshold.

Collisions of 28Si+Al, Cu, and Pb at Elab=14.6 GeV/nucleon were studied at the Brookhaven National Laboratory Alternating Gradient Synchrotron. Charged particle multiplicity was measured over the pseudorapidity interval 0.875≤η≤3.86 with a silicon pad detector. A strong correlation is seen between the multiplicity and the transverse energy measured in the interval -0.5≤η≤0.8. Correlation with the energy going forward after the collision and comparison with calculations indicate that rescattering is required to explain the data. The data are compared under the assumption of Koba-Nielson-Olesen scaling. The measured multiplicity scales approximately with the total number of participant nucleons and less well with the available center-of-mass kinetic energy.Received 12 November 1991DOI:https://doi.org/10.1103/PhysRevC.46.312©1992 American Physical Society

The mass dependence of cross sections for double-isobaric-analog states from pion-induced double-charge-exchange reactions is examined with small-angle data taken at 450 and 500 MeV incident pion energies for several targets. New (pi+, pi-) cross sections are reported for Mg-26, Ti-46, Ti-50, Fe-54, Fe-56, Cr-52, Se-80, Zr-90, Au-197, and Pb-208. The (f7/2)n data are fitted to a two-amplitude model which contains expressions for cross sections for transitions to the DIAS and to nonanalog ground states in the residual nucleus.