J. J. Jarmer

Measurements of ΔσL (np) between 500 and 800 MeV

Abstract A measurement of Δσ L (np), the difference between neutron-proton total cross sections in pure longitudinal spin states, is described. Data were taken for five energies between 500 and 800 MeV, with statistical errors of ≈ 1.5 mb and an estimated normalization error of 6%. The data, combined with other results, show some evidence for an elastic I =0 spin-singlet resonance with mass ∼ 2213 MeV and width ∼ 74 MeV, or a coupled-triplet resonance with similar mass and width.

Beam polarization at the ZGS

Abstract A description is given of a beam polarimeter constructed for use at the Argonne ZGS and later at LAMPF. Details of the absolute calibration of these polarimeters are described. Conclusions for the absolute beam polarization at the ZGS impact a number of past polarized beam experiments, causing normalization changes in some cases of 8–25%. The normalization of some past pp polarization measurements are also affected by these results.

Measurement of Δ σ L and C LL = ( L , L ; 0 , 0 ) in proton-proton scattering between 300 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.

CLL = (L, L; 0, 0) measurements and a structure due to a P partial wave in the pp system☆

Measurements of CLL of pp elastic scattering near θc.m. = 90° at thirteen energies between 300 and 800 MeV are reported. These, together with previous values of CNN, are used to extract values of two quantities, ƒs and ƒt, which contain only spin-singlet and only coupled spin-triplet partial waves, respectively. The ƒs curve, which is not dependent on CLL, exhibits the behavior expected for the previously conjectured 1D2 resonance. The ƒt curve also exhibits a resonance-like behavior, which could be due either to the 3P0 or the 3P2 partial wave.

A neutron hodoscope for medium energy np scattering experiments

Abstract A 24-element plastic scintillation counter hodoscope for np elastic and total cross section measurements at LAMPF is described. Details of construction, electronics, calibration with cosmic ray muons, and a determination of absolute detection efficiency at 289 and 435 MeV are presented.

Dynamic polarization of 19F in a fluorinated alcohol

We have studied microwave dynamic cooling 19F and 1H nuclei in mixtures of 1,1,1,3,3,3‐hexafluoro‐2‐propanol and water, doped with Cr(V) complex. Equal spin temperatures of the two nuclei are produced, and the highest spin polarizations (∼80%) are found in mixtures near the eutectic ratio. The high fluorine content and polarization make this a suitable material for polarized nuclear scattering experiments.

Polarization of a polarized deuteron target from NMR data

A solid polarized deuterated‐ammonia target has been used to measure spin observables for p↘−d↘ elastic scattering at LAMPF. The target polarization was dynamically enhanced to over 30% and monitored with a bridge‐type NMR circuit. A method for determining the vector and tensor polarization is presented which is independent of any assumptions about energy‐level populations. Distortion effects of the NMR circuit are described.

First polarization results from the LAMPF 13C target

A polarized 13C target has been developed and used to measure spin observables for 500‐MeV p‐13C elastic scattering. The material was ethylene glycol, 13C2H6O2, enriched to 99% in 13C. Both the 13C and 1H spins were dynamically polarized in a 3He refrigerator at 2.5‐T magnetic field. The polarization of both species was measured by using the NMR thermal equilibrium calibration technique. In addition, the polarization of 1H was independently measured by p‐p scattering. We describe the target and report on the polarizations obtained and the dependence of the polarizations on integrated beam intensity.

Pion elastic scattering from polarized 13C in the energy region of the P33 resonance.

Analyzing powers [ital A][sub [ital y]] were measured for [pi][sup +] and [pi][sup [minus]] elastic scattering from polarized [sup 13]C at incident pion energies [ital T][sub [pi]] near the [ital P][sub 33] [pi]-nucleon resonance. At [ital T][sub [pi]]=130 MeV, the values of [ital A][sub [ital y]] are significantly different from zero for [pi][sup [minus]] scattering. For [pi][sup +] at [ital T][sub [pi]]=130 MeV and for both [pi][sup [minus]] and [pi][sup +] at all other energies, the [ital A][sub [ital y]] are mostly consistent with zero. Elastic differential cross sections were measured using an unpolarized [sup 13]C target. Both the analyzing-power and cross-section data were compared with predictions using a variety of nuclear structure and reaction models. The analyzing power was found to be strongly sensitive to the quadrupole spin-flip part of the transition. The data of this work complement measurements of the magnetic form factor by electron scattering. The pion [ital A][sub [ital y]] data are not reproduced by calculations using wave functions that fit the magnetic form factor at low momentum transfers.

Pion elastic scattering from polarized [sup 13]C in the energy region of the [ital P][sub 33] resonance

Analyzing powers [ital A][sub [ital y]] were measured for [pi][sup +] and [pi][sup [minus]] elastic scattering from polarized [sup 13]C at incident pion energies [ital T][sub [pi]] near the [ital P][sub 33] [pi]-nucleon resonance. At [ital T][sub [pi]]=130 MeV, the values of [ital A][sub [ital y]] are significantly different from zero for [pi][sup [minus]] scattering. For [pi][sup +] at [ital T][sub [pi]]=130 MeV and for both [pi][sup [minus]] and [pi][sup +] at all other energies, the [ital A][sub [ital y]] are mostly consistent with zero. Elastic differential cross sections were measured using an unpolarized [sup 13]C target. Both the analyzing-power and cross-section data were compared with predictions using a variety of nuclear structure and reaction models. The analyzing power was found to be strongly sensitive to the quadrupole spin-flip part of the transition. The data of this work complement measurements of the magnetic form factor by electron scattering. The pion [ital A][sub [ital y]] data are not reproduced by calculations using wave functions that fit the magnetic form factor at low momentum transfers.