W. J. Briscoe

Analysis of pion photoproduction data

A partial-wave analysis of single-pion photoproduction data has been completed. This study extends from threshold to 2 GeV in the laboratory photon energy, focusing mainly on the influence of new measurements and model-dependence in the choice of parameterization employed above the two-pion threshold. Results are used to evaluate sum rules and estimate resonance photo-decay amplitudes. These are compared to values obtained in the MAID analysis.

The η-meson mass

Abstract The mass of the η meson has been measured through the study of the d p→ 3 He η reaction near threshold, the beam having been calibrated through comparison with three other nuclear reactions. The value obtained is m η =547.30±0.15 MeV/ c 2 , where the error bar includes both systematic and statistical effects. This is much more precise and significantly lower than the Particle Data Group average, through it is consistent with a previous counter experiment.

Photofission of Heavy Nuclei at Energies up to 4 GeV

Total photofission cross sections for 238U, 235U, 233U, 237Np, 232Th, and natPb have been measured simultaneously, using tagged photons in the energy range Egamma=0.17-3.84 GeV. This was the first experiment performed using the Photon Tagging Facility in Hall B at Jefferson Lab. Our results show that the photofission cross section for 238U relative to that for 237Np is about 80% over the entire energy range, implying the presence of important processes which compete with fission. If we assume that for 237Np the photofission probability is equal to unity, we observe a significant shadowing effect, starting below 1.5 GeV.

Measurement of neutron detection efficiencies in NaI using the Crystal Ball detector

A light-emitting apparatus according to the present invention includes: a board on which a plurality of light source units are provided; a partition member provided on the board and enclosing each of the light source units; and a fixing member arranged in a boundary portion between two or more light source units that are adjacent to each other and fixing the board and the partition member.

Calibration of neutron counters from 83 to 290 MeV

The eight neutron detectors described in the preceding paper have been calibrated with tagged neutrons from the reaction π−d → nn for Tn = 83–290 MeV. The neutron detection coefficient λ is (8.7 ± 0.2) × 10−3/(cm path length) at 83 MeV and decreases monotonically to (7.6 ± 0.5) × 10−3/(cm path length) at 290 MeV. Measurements were made repeatedly for different configurations to show the internal consistency of the data. Our results are in good agreement with the calibration data for neutron counters reported by Betti et al. but not with the work of Strong et al. Our data support the energy dependence of the efficiencies calculated by the Kent State University neutron efficiency code.

Cross-section measurements of p + d → 3He + π0 and p + d → 3H + π+ at intermediate energies

We present differential cross sections for p+ d → 3He + π0 at Tp = 300, 350, 400, 425, 450, 470 and 500 MeV, and for p + d → 3H + π+ at 500 MeV, mostly near θπ (c.m.) = 48° and 98°. The ratio dσ(pd → 3H π+)/dσ(pd → 3Heπ0) for identical four momentum transfer at 500 MeV is found to be 2.21 ± 0.17 to 2.57 ± 0.34, depending on angle. The dependence of the invariant matrix element squared |M|2 on the relativistic invariants t and s is examined; for a given value of t, |M|2 is almost independent of s for Tp between 350 and 800 MeV.

Charge-symmetry violation in pion scattering from three-body nuclei

We discuss the experimental and theoretical status of charge-symmetry violation (CSV) in the elastic scattering of pi+ and pi- on 3H and 3He. Analysis of the experimental data for the ratios r1, r2, and R at Tpi = 142, 180, 220, and 256 MeV provides evidence for the presence of CSV. We describe pion scattering from the three-nucleon system in terms of single- and double-scattering amplitudes. External and internal Coulomb interactions as well as the Delta-mass splitting are taken into account as sources of CSV. Reasonable agreement between our theoretical calculations and the experimental data is obtained for Tpi = 180, 220, and 256 MeV. For these energies, it is found that the Delta-mass splitting and the internal Coulomb interaction are the most important contributions for CSV in the three-nucleon system. The CSV effects are rather sensitive to the choice of pion-nuclear scattering mechanisms, but at the same time, our theoretical predictions are much less sensitive to the choice of the nuclear wave function. It is found, however, that data for r2 and R at Tpi = 142 MeV do not agree with the predictions of our model, which may indicate that there are additional mechanisms for CSV which are important only at lower energies.

Measurement of k-p → ηΛ near threshold

We present measurements of the differential and total cross sections and the {Lambda} polarization for the reaction K{sup -}p{yields}{eta}{Lambda} from threshold to p{sub K}-=770 MeV/c, with much better precision than previous measurements. Our cross-section data show a remarkable similarity to the SU(3) flavor-related {pi}{sup -}p{yields}{eta}n cross-section results. The reaction K{sup -}p{yields}{eta}{Lambda} at threshold is dominated by formation of the intermediate {Lambda}(1670)1/2- state.

Elastic electron scattering from the isotopes 35Cl and 37Cl

Abstract The charge structure of 35Cl and 37Cl has been investigated using the technique of elastic electron scattering. Data were collected at the University of Saskatchewan Linear Accelerator Laboratory with incident electron energies of 116 and 194 MeV and at scattering angles ranging from 45 to 140°. The data span a range of q between 0.60 and 1.71 fm−1. Phase-shift fits to a threeparameter Fermi distribution yield model-dependent rms charge-radius values of 3.388 ±0.015 fm for 35Cl and 3.384±0.015 fm for 37Cl.

Elastic π±p scattering from 378 to 687 MeV/c☆

Abstract Differential cross sections for π±p→π±p have been measured at Pπ between 378 and 687 MeV/c at 9 angles in the range −0.8⩽cosθc.m.⩽0.6. Scattered pions and recoil protons were detected in coincidence using scintillation counter hodoscopes. For almost all of the data the statistical and normalization uncertainties are each less than 2%. Our measurements are compared with existing data and the results of recent partial wave analyses.