D.C. Healey

NMR measurements on the triumf polarized deuterium target

Abstract The NMR system and the polarization measurements of the TRIUMF polarized deuterium target are described. The NMR tuned circuit is kept resonant at all frequencies to allow for a high gain in the rf amplifiers and to permit the measurement of the real part of the NMR signal. A Starburst (J-11) and an LSI-11 are used to process the NMR signal at a high sample rate. A synthesizer under the control of an 8085 based microprocessor (TRIMAC) provides the rf sweep. Vector polarizations between −0.33 and −0.40 were routinely achieved during a four week run in the TRIUMF M11 pion beamline with a statistical uncertainty of 3.4% and a systematic uncertainty of 5%.

The frozen spin polarized proton target at TRIUMF for intermediate energy neutron scattering

Abstract A polarized proton target with a volume of 55 cm 3 was constructed at TRIUMF to study neutron induced reactions. The polarizable protons were contained in the molecules of 1-butanol that was frozen in the form of beads and placed in the mixing chamber of a vertical dilution refrigerator. The target system was operated about 2000 h for a high precision neutron scattering experiment to test charge symmetry breaking. The highest polarization achieved was −0.97. The relaxation time was typically 150 h in a magnetic field of 0.257 T and at a temperature of 60 mK.

Proton target polarization measured with a polarized neutron beam at 477 MeV

Abstract The polarization of a proton target is determined with elastic neutron-proton scattering at 477 MeV. The results agree well with the nuclear magnetic resonance measurements at the error level of 4%.

The frozen spin orientation of deuterium nuclei irradiated at radio-frequencies

A dynamically polarized deuterium target was constructed to determine the second-order analyzing power T20 in π−d elastic scattering. The required deuterium alignment can be enchanced by high-intensity rf irradiation of oriented deuterium nuclei. A method was developed to obtain the target-averaged alignment from NMR spectra. Of the irradiation schemes that were tested experimentally, the rf burning of the pedestal area at the edge of the NMR spectrum provided the largest alignment increase (more than a factor 1.5). For this spin reorientation lifetimes longer than 50 h were measured.

Parity violation in P‐P scattering at TRIUMF

The TRIUMPF experiment 497 which will measure the (weak) parity violating component of the nucleon‐nucleon interaction with proton‐proton quasi‐elastic scattering at 223 MeV is described. The longitudinal analyzing power Az=(σ+−σ−)/(σ++σ−) where σ+ and σ− are the scattering cross sections for positive and negative beam helicity, respectively, with an expected precision of ±2×10−8. (AIP)

Parity violation in p-p scattering

Abstract An outline is given of an experiment to measure parity violation in p-p scattering at 230 MeV at TRIUMF. The parity-violating longitudinal analysing power A z will be measured to a precision of 2×10 −8 and will isolate the parity-violating 3 P 2 − 1 D 2 partial wave amplitude.

Direct measurement of the tensor polarization of a polarized deuteron target

Abstract The tensor alignment p zz of a polarized deuteron target was measured directly for the first time. The measurement utilizes the tensor analyzing power T 20 of the πd to 2p reaction at 90° (c.m.), which is well determined from partial wave analysis and consistent theoretical predictions. The resulting value of p zz agrees well with that calculated from the vector polarization p z obtained from NMR techniques.

Measurement of charge symmetry breaking in np elastic scattering at 350 MeV

TRIUMF Experiment 369, a measurement of charge symmetry breaking in np elastic scattering at 350 MeV, has completed data taking. Scattering asymmetries were measured with a polarized (unpolarized) neutron beam incident on an unpolarized (polarized) frozen spin target. Coincident scattered neutrons and recoil protons were detected by a mirror symmetric detection system in the center‐of‐mass angle range from 50°–90°. A preliminary result for the difference of the zero‐crossing angles, where analyzing powers cross zero, is Δθcm =0.445°±0.054°(stat.)±0.051°(syst.) based on fits over the angle range 53.4°≤θcm≤86.9°. The difference of the analyzing powers ΔA≡An−Ap, where the subscripts denote polarized nucleons, was deduced with dA/dθcm=(−1.35±0.05)×10−2 deg−1 to be [60±7(stat.)±7(syst.)±2(syst.)] ×10−4.

Parity violation in proton-proton scattering

Abstract Measurements of parity-violating longitudinal analyzing powers (normalized asymmetries) in polarized proton-proton scattering provide a unique window on the interplay between the weak and strong interactions between and within hadrons. Several new proton-proton parity violation experiments are presently either being performed or are being prepared for execution in the near future: at TRIUMF at 221 MeV and 450 MeV and at COSY (Kernforschungsanlage Julich) at 230 MeV and near 1.3 GeV. These experiments are intended to provide stringent constraints on the set of six effective weak meson-nucleon coupling constants, which characterize the weak interaction between hadrons in the energy domain where meson exchange models provide an appropriate description. The 221 MeV is unique in that it selects a single transition amplitude ( 3 P 2 - 1 D 2 ) and consequently constrains the weak meson-nucleon coupling constant h ϱ pp . The TRIUMF 221 MeV proton-proton parity violation experiment is described in some detail. A preliminary result for the longitudinal analyzing power is A z = (1.1 ± 0.4 ± 0.4) × 10 −7 . Further proton-proton parity violation experiments are commented on. The anomaly at 6 GeV/c requires that a new multi-GeV proton-proton parity violation experiment be performed.

The TRIUMF parity violation experiment

An experiment (E497) is underway at TRIUMF to measure the angle-integrated, parity violating longitudinal analyzing power, A{sub z}, in proton-proton elastic scattering, to a precision of {plus_minus}0.2{times}10{sup {minus}7}. The experiment uses a 221 MeV longitudinally polarized proton beam incident on a 40 cm liquid hydrogen target. The beam energy is carefully chosen so that the contribution to A{sub z} from the J=0 parity mixed partial wave ({sup 1}S{sub 0}{minus}{sup 3}P{sub 0}) integrates to zero over the acceptance of the apparatus, leaving the experiment sensitive mainly ({gt}95{percent}) to A{sub z} arising from the {sup 3}P{sub 2}{minus}{sup 1}D{sub 2}, J=2 wave. To minimize sources of systematic error, the TRIUMF ion source and cyclotron parameters have been refined to the extent that helicity correlated beam changes are at an extremely low level, and specialized instrumentation on the E497 beamline is able to measure residual helicity correlated modulations to a precision consistent with the goals of the experiment. A data taking run in February-March, 1997 logged approximately 12{percent} of the desired data and produced a preliminary result, A{sub z}=(1.1{plus_minus}0.4{plus_minus}0.4){times}10{sup {minus}7}, where the error is statistical only. {copyright} {ital 1997 American Institute of Physics.}