R.L. Boudrie

Neutron-proton radius differences and isovector deformations from π+ and π− inelastic scattering from 18O

Abstract π+ and π− elastic and inelastic scattering from 18O have been measured at T(π)=164 MeV. Consistent with the results at 230 MeV, it is found that the ratio σ(π − ) σ(π + ) for the 21+ state is 1.86(16), while for the 31− state it is 0.89(6). These results are interpreted as indicating differences in neutron and proton deformations characterizing the 21+ transition and partial neutron blocking for the 31− transition. Optical model analysis of elastic scattering leads to the conclusion that 〈r n 2 〉 1 2 −〈r p 2 〉 1 2 =0.03(3) fm .

Observation of isospin mixing in 12C near 19.5 MeV excitation

Abstract A strongly isospin-mixed doublet has been found in 12C near 19.5 MeV excitation energy in a comparison of π− and π+ inelastic scattering at 162 MeV. The π+ and π− comparison technique may be universally employable in self-conjugate nuclei to extract isospin-mixing matrix elements.

Observation of enhanced excitation of 12C by inelastic pion scattering on the (3,3) pion-nucleon resonance

Abstract Pion inelastic scattering on 12 C to states at an excitation energy of approximately 19 MeV shows a strong enhancement at an incident pion energy near the pion-nucleon (3,3) resonance. This resonance may therefore provide a mechanism for the selective enhancement of inelastic transitions.

0. 8 GeV p+/sup 208/Pb elastic scattering and the quantity. delta. r/sub n/p

Analyses of 0.8 and 1 GeV p+/sup 208/Pb elastic angular distribution data have obtained neutron-proton root-mean-square radius differences (..delta..r/sub n/p) which are not consistent. Therefore, the 0.8 GeV experiment was repeated using a high resolution spectrometer. The new higher precision data are consistent with the older data, apart from a 15% overall normalization difference. A second order Kerman-McManus-Thaler optical model analysis of the new data, using a model-independent neutron density, yields ..delta..r/sub n/p=0.14 +- 0.04 fm, in good agreement with the most recent result obtained (0.16 +- 0.05 fm) from a similar analysis of the older 0.8 GeV data. In addition, the elastic angular distribution was extended to 42.5/sup 0/ center of mass in order to explore the momentum transfer region from 3.5 to 5.3 fm/sup -1/. Although the familiar diffraction pattern persists to 42.5/sup 0/, it was not possible within the framework of our application of the Kerman-McManus-Thaler optical model to fit the data even qualitatively at the larger momentum transfers.

0.8-GEV P Pb-208 ELASTIC SCATTERING AND THE QUANTITY DELTA - R (N P)

Analyses of 0.8 and 1 GeV p+/sup 208/Pb elastic angular distribution data have obtained neutron-proton root-mean-square radius differences (..delta..r/sub n/p) which are not consistent. Therefore, the 0.8 GeV experiment was repeated using a high resolution spectrometer. The new higher precision data are consistent with the older data, apart from a 15% overall normalization difference. A second order Kerman-McManus-Thaler optical model analysis of the new data, using a model-independent neutron density, yields ..delta..r/sub n/p=0.14 +- 0.04 fm, in good agreement with the most recent result obtained (0.16 +- 0.05 fm) from a similar analysis of the older 0.8 GeV data. In addition, the elastic angular distribution was extended to 42.5/sup 0/ center of mass in order to explore the momentum transfer region from 3.5 to 5.3 fm/sup -1/. Although the familiar diffraction pattern persists to 42.5/sup 0/, it was not possible within the framework of our application of the Kerman-McManus-Thaler optical model to fit the data even qualitatively at the larger momentum transfers.

On-Line Polynomial Optimization for High Resolution Spectromieters

A method has been developed to use a standard linear least squares routine to optimize various calculated quantities for the high resolution magnetic spectrometers of EPICS and HRS at LAMPF. Calculated quantities, such as x position at the target, can be expressed as polynomials of other calculated quantities and positions and angles directly determined by wire chambers. For each event (particle through the spectrometer) that satisfies predetermined limits, these coordinates (position, angle, momentum, etc.) are written to a disk file. A program which includes a linear least squares routine can then take an unlimited number of these events and do a fit to a polynomial consisting of terms which are up to fourth order in the coordinates of these events.