A. Villari

Differential cross sections and analysing powers for PP → π−π+ and K−K+ from 360 to 1550 MeV/c

Abstract Analysing powers and differential cross sections for p p → π − π + and p p → K − K + have been measured over the full angular range using a polarised target at LEAR at 20 beam momenta from 360 to 1550 MeV/c. Discrepancies in the normalisation of earlier d σ/ d Ω data at low momenta are clarified. Above 1000 MeV/c, A0N results confirm values close to +1 over most of the angular range for both reactions, in excellent agreement with earlier data of lower statistics. Below 1000 MeV/c, where the analysing power is measured for the first time, large variations of A0N with energy and angle are present.

Asymmetry in p¯p elastic scattering

Abstract Asymmetries A 0 n have been measured at LEAR for s ¯ s elastic scattering for 15 beam momenta from 497 to 1550 MeV/ c .

Measurement of antiproton-proton small-angle elastic scattering at low momentum

Abstract Two high statistics measurements of antiproton-proton small-angle elastic scattering, at p = 233 MeV/c and p = 272 MeV/c, are presented. The measurements were carried out at the LEAR facility at CERN. By the Coulomb-nuclear interference method, values are obtained for the real-to-imaginary ratio ρ of the pp forward nuclear scattering amplitude and for its exponential slope b: ρ = + 0.041 ± 0.026 and b = 71.5 ± 4.5 (GeV/c)−2 at 233 MeV/c and ρ = −0.014 ± 0.027 and b = 47.7 ± 2.7 (GeV/c)−2 at 272 MeV/c. The method to derive these values is discussed in detail and so are the uncertainties contributing to their systematic error. The results are compared with predictions from forward dispersion relation calculations and with predictions from pp potential models.

Measurement of dσ/dΩ and Aon in pp elastic scattering between 497 and 1550 MeV/c

Measurements have been made of the differential cross section and asymmetry Aon for pp elastic scattering at 15 incident momenta between 497 MeV/c and 1550 MeV/c. The angular range where both particles have enough energy to traverse target and setup has been covered. The results are compared with predictions of various NN potential models. None of these models fully explains the present results, although the general trend of the data is predicted correctly.

First measurement of Donon in pp elastic scattering

Abstract The depolarization parameter D onon in p p elastic scattering has been measured at LEAR for thirteen momenta between 679 and 1550 MeV/c in the backward angular region. Striking disagreement with theoretical models is observed.

Real-to-imaginary ratio of the p̄p forward elastic scattering amplitude at 550, 757, and 1077 MeV/c

Abstract The ratio of the real to the imaginary part of the pp forward elastic-scattering amplitude ϱ has been measured at 550, 757, and 1077 MeV/c at LEAR, using the Coulomb-nuclear interference method. The results obtained for ρ and b, the nuclear slope, are ϱ = 0.084 ± 0.051 and b = 20.9 ± 2.1 (GeV/c)−2 at 550 MeV/c, ϱ = 0.102 ± 0.043 and b = 18.0 ± 0.5 (GeV/c)−2 = at 757 MeV/c, and ϱ = 0.059 ± 0.035 and b = 15.2 ± 0.3 (GeV/c)−2 at 1077 MeV/c.

Reconstruction of the momentum of a particle moving in an axially symmetric magnetic field

Abstract We describe a method which provides the coordinates along the trajectory of a particle traversing an axially symmetric magnetic field. The momentum of the particle is evaluated with a simple algorithm when the detectors which measure the coordinates of the particle trajectory are of cylindrical shape.

Measurement of the polarization of the proton-proton elastic reaction at small scattering angles between 940 and 2440 MeV

Abstract We have measured the asymmetry of elastic pp scattering at small scattering angles (30–100 mrad) in the Coulomb-nuclear interference region, using the polarized proton beam of Saturne II, a segmented scintillator active target, and two telescopes of multiwire proportional chambers. Results are given at four energies — 940, 1000, 1320 and 2440 MeV-and are compared with phase-shift calculations.

Asymmetry measurements in antiproton-proton annihilation into two mesons at low energies

Abstract Analysing power and differential cross-section have been measured for the reactions p p →π − π + , p p →K − K + by the SING Collaboration (PS172) at LEAR, using a polarized target. Preliminary results of Aon are presented, at 12 momenta from 500 to 1500 MeV/c. They show very large asymmetries, and a remarkable variation with energy in the newly explored low momentum region.

A measurement of the polarization parameter in π−p→K+Σ− backward scattering at 3.5 GeV/c

Abstract We have measured the polarization parameter in π − p→K + Σ − backward scattering at 3.5 GeV/ c incident momentum, in the u -range −0.6 u 2 . The apparatus consisted of a polarized target in a spectrometer magnet, counter hodoscopes for time-of-flight measurements, a large water Cerenkov counter for kaon tagging, and wire spark chambers. After identification of the kaons, the reaction was selected by a missing-mass technique. An isospin analysis has been carried out to separate the contributions of the various isospin exchange amplitudes in the u -channel.