Ludgate, George Arthur (1977)
Measurement of Wolfenstein Parameters for the p-p system to determine accurate phase shifts near 500 MeV.
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The Wolfenstein p-p parameters P, D and R have been measured at the four laboratory scattering angles 6, 9, 15 and 24 degrees together with a single R' measurement at the 15 degree angle. Statistical error on each measurement is typically 0.025. A 518 MeV polarized proton beam was produced at TRIUMF from a Lamb Shift source and free p-p scattering was observed from a liquid hydrogen target. Components of the initial and final polarizations were measured; the former by scintillator telescopes viewing a CE
target, the latter bya large solid angle acceptance (carbon) Polarimeter utilizing multiwire proportional chambers. A separate experiment was undertaken to calibrate the Polarimeter at 9 energies and the results from the analysis of this data were used in the final calculation of the Wolfenstein parameters. Time-of-flight and momentum analysis were undertaken to remove inelastic protons and pions above threshold. Straight tracks through the final Polarimeter were rejected by beam defining counters for overall efficiency of the experiments.
A superconducting solenoid was used in the R and R' measure-ments to precess the vertical primary beam polarization by +/- 90 degrees into the horizontal plane before the hydrogen target. The polarization of the primary beam was reversed at its source for the four parameter's measurements allowing data to be recorded for two polarization orientations. The R' parameter required a precession magnet in the secondary beamline to precess the longitudinal polarization into the horizontal plane.
The measured Wolfenstein parameters have been used in asingle energy phase shift analysis at 515 MeV to improve the precision of the isovector nucleon-nucleon phases.
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Institution: University of London, Bedford College (United Kingdom).