M. Simonius

A quantitative monitor for beam intensity and polarization profiles

Abstract A beam profile monitor is described which permits a rapid quantitative determination of the beam intensity profiles I(x), I(y) in two directions (x, y) perpendicular to the beam, as well as the proton beam-polarization profiles Py(x), Py(y), Px(y) and Px(x) for a 50 MeV proton beam. The device consists of two wheels which move thin strips of graphite through the beam. Four scintillation detectors are used to detect protons elastically scattered from the graphite targets. An encoder digitizes the position of the targets associated with each detected proton. The scanner is interfaced with a computer. Performance figures for the scanner are given. Typically, when a 0.1 μA beam of 3 mm diameter is interrupted by the targets during 10% of the time, a 1 min measurement suffices to determine the center of the beam to ±4 μm and the beam polarization to ±0.3%.

Effects of transverse polarization components in parity tests with longitudinally polarized nucleons

Abstract In the study of parity violation by the scattering of longitudinally polarized spin 1 2 particles, systematic errors arise from the presence of small polarization components perpendicular to the beam. A quantitative treatment of these errors is presented. It is shown that non-uniform polarization distributions over the beam profile give sizeable effects even if the average transverse polarization vanishes. Methods are presented which permit accurate correction of the parity measurements for the presence of transverse polarization components. It is shown that the necessary information can be obtained by measuring four suitably chosen one-dimensional intensity and polarization distributions within the beam. Finally, possible origins of the non-uniform polarization distributions are outlined.

Measurement of parity nonconservation in proton-deuteron scattering at 43 MeV

Abstract Parity nonconservation has been studied in the interaction of longitudinally polarized protons with deuterons at 43 MeV. Protons from pd elastic scattering and from part of the pd break-up spectrum were detected in the angular range 24°–61° (laboratory frame). The longitudinal analyzing power is found to be (+0.4±0.7)×10 −7 ). For comparison with theory, the angular acceptance function of the apparatus for break-up protons is also reported.

Parity violation and quark-diquark scattering in high energy proton-nucleon total cross sections

Abstract We reexamine a quark-diquark scattering model of the parity violating helicity dependence A L in the high energy proton-nucleon total cross section, which seemed to explain the unexpectedly large value of A L = 2 × 10 −6 found experimentally at 6 GeV/ c and predicted further continuous increase of the effect with energy. We find that if the part of the strong amplitude that dominates the weak-strong interference in this model is included also in the normalizing strong total cross section, the latter rises unphysically with energy, and A L is reduced to −7 as in more conventional calculations.