We have made measurements of polarization in π−p elastic scattering, with emphasis over the backward region, at 1.60 to 2.28 GeVc. The results indicate the absence of u-channel dominance in the backward region, as was observed in the case of π+p scattering. Comparisons have been made with predictions of various phase-shift analyses which show that the agreement is generally very poor in the backward region.
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Analyzing powers of pion-proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS as well as a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for pi+ p scattering, and at 67.3 and 87.2 MeV for pi- p scattering. These new measurements constitute a substantial extension of the polarization data base at low energies. Predictions from phase shift analyses are compared with the experimental results, and deviations are observed at low energies.
Analyzing power for PI+ P elastic scattering at incidient kinetic energy 87.2 MeV from the data set 1.
Analyzing power for PI+ P elastic scattering at incidient kinetic energy 68.4 MeV from the data set 1.
Analyzing power for PI+ P elastic scattering at incidient kinetic energy 57.2 MeV from the data set 1.
Results on polarization in π − p and π + p forward elastic scattering at 10, 14 and 17.5 GeV/ c are presented.
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Measurements of the polarization parameters and angular distributions are reported for π±p elastic scattering at 100 GeV/c and for pp elastic scattering at 100- and 300-GeV/c incident momentum. The π±p data cover the kinematic range 0.18≤−t≤1.10 GeV2 and are in agreement with current Regge-model predictions. The pp data cover the kinematic range 0.15≤−t≤1.10 GeV2 and 0.15≤−t≤2.00 GeV2 at 100 and 300 GeV/c, respectively, and are found to be consistent with absorption-model predictions.
THESE ANGULAR DISTRIBUTIONS AND POLARIZATION PARAMETERS ARE TABULATED IN THE RECORD OF THE EARLIER BRIEF REPORT OF THIS EXPERIMENT USING PION BEAMS: I. P. AUER ET AL., PRL 39, 313 (1977).
THESE ANGULAR DISTRIBUTIONS AND POLARIZATION PARAMETERS ARE TABULATED IN THE RECORD OF THE EARLIER BRIEF REPORT OF THIS EXPERIMENT USING A PROTON BEAM: J. H. SNYDER ET AL., PRL 41, 781 (1978) AND PRL 41, 1256(E) (1978).
Analyzing powers for π−p elastic scattering have been measured at TRIUMF using the CHAOS spectrometer and a spin-polarized target. These data were collected at a bombarding energy of Tπ=279MeV and cover an angular range of 53<~θc.m.π<~180°. There is good agreement between these data and the latest partial wave analysis from the VPI/GWU group.
Analysing power measurement.
The asymmetry parameter A in π−p elastic scattering at incident pion laboratory kinetic energies Tπ of 98, 238, and 2922 MeV and in π−p charge-exchange scattering π−p→π0n at Tπ=238, 292, and 310 MeV have been measured over a wide range of scattering angles (typically from about 60° to 130° c.m.) with a polarized proton target. The data have been used in an energy-independent phase-shift analysis to improve the precision of the pion-nucleon phase shifts, to set new limits on violation of isospin conservation in the pion-nucleon S wave, and to confirm significant charge dependence in the P32 wave.
Axis error includes +- 0.0/0.0 contribution (?////BACKGROUND SUBTRACTION SMALL).
Axis error includes +- 0.0/0.0 contribution (?////BACKGROUND SUBTRACTION SMALL).
Axis error includes +- 0.0/0.0 contribution (?////BACKGROUND SUBTRACTION SMALL).
We have measured the polarization in π − backward elastic scattering at 2.22, 2.46, 2.71 and 3.50 GeV/ c incident momenta, in the u -range−1.0 ≦ u ≦0.1 (GeV/ c ) 2 . The experiment used a polarized proton target and detected both pions and protons. We have found large discrepancies between the new data and the result of even the latest phase-shift analysis.
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The polarization parameter in π − p elastic scattering has been measured in the backward angular region at an incident momentum of 6 GeV/ c . The measurements cover the range of four momentum transfer u = 0 to −1 (GeV/ c ) 2 , and were obtained with a high intensity pion beam, a butanol polarized proton target, and arrays of scintillation counter hodoscopes. The polarization is different from zero, in contradiction to the prediction of the naive one trajectory Regge-exchange model. It increases positively with the four-momentum transfer u, reaching a maximum of about 0.4 at u ≈ −0.3 (GeV/c)2. It then decreases and becomes slightly negative beyond u ≈ −0.5 (GeV/c)2. A variety of baryon exchange models are briefly reviewed and none are found to be in complete agreement with all the experimental data.
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We report measurements of the polarization parameters in π+p and π−p elastic scattering at an incident momentum of 100 GeV/c. The results cover the range 0.18<~−t<~1.4 GeV2 and are in agreement with current Regge-model predictions.
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