E. Heer

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.

p̄p total cross sections below 420 MeV/c

Abstract pp total cross sections have been measured from 220 to 413 MeV/ c in small (⩽ 10 MeV/ c ) steps of momentum with statistics of ± 0.5 %. There is no evidence for structure in the cross section, and a limit of 8 mb MeV/ c 2 is set with 90% confidence on the strength of any narrow resonance down to 250 MeV/ c .

Evidence against the S-meson

Abstract Measurements are reported of pp total cross sections from 388 to 599 MeV/c in small momentum steps. Statistical errors are typically ±0.4%and the normalisation uncertainty is ±0.7%. There is no evidence for the “S-meson”.

Measurement of the analysing power and the differential cross section of the pp charge-exchange reaction at LEAR

Abstract As part of a programme to study the spin structure of the p p→ n n channel, we have measured the analysing power A 0 n and the differential cross section at an incident antiproton beam momentum of 704 MeV/ c . The analysing power exhibits a remarkable angular dependence, which is poorly reproduced by the existing potential models.

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 the analyzing power of the charge-exchange reaction in the momentum range 546-875 MeV/c at LEAR

Abstract Results are given for the analysing power of the p p→ n n charge-exchange reaction at four incident beam momenta. The measurement is part of an experimental programme to study the spin structure of this reaction at LEAR. The analyzing power shows strong angular and energy dependence, which at present is not reproduced by the existing meson-exchange 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.

Measurement of the analysing power of the charge-exchange pp → nn reaction in the momentum range 546–1287 MeV/c at LEAR

Final results of the measurement of the analysing power AOn of the pp → nn reaction are presented. Eight measurements in the range 546–1287 MeV/c incoming p momentum have been performed over the full angular range using a solid polarized proton target and the Low Energy Antiproton Ring (LEAR) at CERN antiproton extracted beams.

Polarization at small angles in antiproton-carbon elastic scattering at LEAR energies

Abstract A double-scattering experiment of antiprotons on carbon has been carried out at the Low-Energy Antiproton Ring (LEAR) at CERN, to measure the polarization parameter A p C in antiproton-carbon elastic scattering at small angles. The polarization parameter has been inferred from the azimuthal distribution of the antiprotons after the second scattering. Data have also been collected with a liquid-hydrogen target as the second scatterer, thus allowing the sign of A p C to be determined. The experiment has been performed at two momenta of the extracted antiproton beam, 800 and 1100 MeV/c. A small positive value of the polarization has been observed, compatible with energy independence and a linear increase with the momentum transfer q. Parametrizing A p C as acq, we get ac = +0.72 0.10+0.09(GeV/c)−1. This result is compared with potential model predictions for NN amplitudes through a Glauber theory calculation.

Measurement of ΔσL in pp scattering between 200 and 583 MeV

Abstract The main structure around m = 2.15 GeV first observed by the Argonne group in the spin-dependent total cross section Δσ L is confirmed in the energy range available at SIN. A simultaneous study of the scattered particles at small angles has been carried out with success and gave the spin-correlation parameter A 00 kk for the pp elastic scattering and for the reaction pp → π + d. The contribution of the 3-body reactions to this spin-dependent total cross section has been deduced and found to be lower than the contribution of the π + d reaction even at 583 MeV.