William B. Cottingame

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.

Studies of the pion double-charge exchange reaction 18O(π+, π−)18Ne☆

Abstract Results of the first measurement if the excitation function of the cross section dσ/dΩ for the pion double charge exchange reaction across the (3,3) π-nucleon resonance are reported. Data from the reaction 18 O(π + , π − ) 18 Ne to the double isobaric analog state at an angle of 5° are presented which show strong structure as a function of pion energy, in contrast to the previous limited data. The measurements were made with the EPICS facility at LAMPF which was modified to allow for data-taking at small angles.

Indication of Δ-hole configurations in 12C(15.11 MeV)

Abstract A strong energy dependent enhancement is seen in inelastic pion scattering from 12 C to the 1 + , T = 1 state at 15.11 MeV, but not to the 1 + , T = 0 state at 12.71 MeV. This enhancement may be interpreted as evidence for the direct excitation of delta-hole (Δ-h) components in the wave function of the T = 1 state. The required Δ-h amplitude is estimated and found to be in agreement with calculations of Bohr and Mottelson.

Measurement of isospin mixing between the 1+ doublet in 12C using pion inelastic scattering ☆

Abstract Pion inelastic scattering has been used to extract the off-diagonal charge dependent matrix element, H01, between the Jπ = 1+ doublet of states at 12.71 (T = 0) and 15.11 (T = 1) MeV in 12 C . The reported measurements yield a value, H01 = 148 ±29 keV, in good agreement with recent electromagnetic measurements.

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.

Diffractive angular distribution for /sup 16/O(. pi. /sup +/,. pi. /sup -/)/sup 16/Ne(g. s. )

The 164-MeV angular distribution for the non-analog double charge exchange reaction /sup 16/O(..pi../sup +/, ..pi../sup -/)/sup 16/Ne(g.s.) has been measured and is found to be basically diffractive. This is contrasted with the previously measured analog distribution /sup 18/O(..pi../sup +/, ..pi../sup -/)/sup 18/Ne (double isobaric analog) which is not diffractive.

MEASUREMENT OF DELTA SIGMA-l AND C (L, L) = (L, L : 0, 0) N PROTON PROTON SCATTERING BETWEEN 300-MEV AND 800-MEV

Measurements are reported of the difference ..delta..sigma/sub L/ between proton-proton total cross sections for parallel and antiparallel spin states and of the parameter C/sub L/L for proton-proton elastic scattering near 90/sup 0/, for thirteen energies between 300 and 800 MeV. The ..delta..sigma/sub L/ results agree well with previous ANL ZGS and SIN data, but disagree with recent results from TRIUMF. Attempts to understand the cause of the discrepancy have been unsuccessful, but possible sources are discussed. The ..delta..sigma/sub L/ and C/sub L/L results have been used with other experimental data to extract quantities which depend only on spin-singlet, coupled spin-triplet, and spin-triplet partial waves. Structure is found in these quantities, which appears to be associated with the resonantlike /sup 1/D/sub 2/ and /sup 3/F/sub 3/ partial waves. Additional similar structure is also found, which may be due either to the /sup 3/P/sub 0/ partial wave or the (/sup 3/P/sub 2/, /sup 3/F/sub 2/) partial-wave pair.

Qualielastic scattering of pions from 12C and 40,44,48Ca

Measurements have been made of the differential cross section d2σ/dΩdE for π+ scattered from 12C aNd 40,44,48Ca in the energy region corresponding to quasielastic scattering, using the EPICS facility at LAMPF. Data were taken at 180 Mev, 60°, And 290 Mev, 60° and 120°. Corrections were made for muon contamination, using information found on muons seen in π‐p scAttering measurements. A sample of the data is shown in Fig. 1. The rest of the for each of the two angles are very similar in character to this. Within the errors, no simple systematic effects can be seen either in the Ca isotope cross sections or in the π−/π+ ratios. These results are being studied using calculations based on pion scattering from a Fermi gas of nucleons.

Measuring isospin mixing in nuclei using π± inelastic scattering

A new strongly isospin‐mixed doublet has been found in 12C near 19.5 MeV. in a comparison of π− and π+ inelastic scattering at 180 MeV, The present techniques may be universally employable, at least in self‐conjugate nuclei, in extracting isospin‐mixing matrix elements.