Y. Onel

A proton and neutron beam polarimeter at SATURNE II

Abstract A beam polarimeter using CH 2 and carbon targets has been used to measure proton and neutron beam polarization in the energy range 0.4–2.8 GeV in one of the beam lines at the SATURNE II accelerator. The analyzing power for np-scattering is calibrated against the known analyzing power for pp-scattering by using the polarized deuteron beam to measure simultaneously the asymmetries for scattering of quasifree protons and neutrons in the deuterons. A low level of systematic errors is achieved by pulse to pulse polarization reversal at the ion source of the accelerator, and by measuring left and right scattering simultaneously. The detailed operation procedure and the beam polarizations measured during all experiments from 1981 to 1984 are presented.

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 .

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 the total cross section difference ΔσT(pp) in the energy range from 0.43 to 2.4 GeV

Abstract The SATURNE II polarized proton beam and the Saclay frozen spin polarized proton target were used to measure the total cross section difference Δσ T = −2 σ 1 tot at 26 energies between 0.43 and 2.4 GeV. Here Δσ T is the total cross section difference for transverse beam and target spins parallel and antiparallel, respectively, and σ 1tot is one of spin-dependent terms in the total cross section σ tot . The energy dependence of Δσ T below 1 GeV shows similar structures as for Δσ L . An additional minimum appears at about 1.3 GeV, which involves a structure in singlet spin partial waves.

Measurement of the spin correlation parameter A00kk for pp elastic scattering in the energy range 0.72–1.1 GeV

The spin correlation parameter A00kk (pp) has been measured in the angular region 45°<θCM<90° at 0.719, 0.834, 0.874, 0.934, 0.995 and 1.095 GeV using the SATURNE II polarized proton beam incident on a polarized target. The parameters A00nn(pp and A00sk(pp) were measured at 0.874 in the same angular region.

Measurement of the spin correlation parameter Aoonn for pp elastic scattering in the energy range from 0.83 to 1.1 GeV

Abstract The spin correlation parameter A oonn (pp) and the analyzing power A oono (pp) have been measured in the angular region 45° θ CM

Measurement of the pp analyzing power Aoono in a large angular region between 0.88 and 2.7 GeV

Abstract The pp analyzing power was measured using the SATURNE II polarized proton beam and the Saclay frozen spin polarized target. The measurements at 0.88 and 1.1 GeV were carried out in the angular region θ CM from 28° to ≅50° and complete our previous measurements from 45 ° to 90°. Above 1.1 GeV the measurements presented here cover both regions, extending from θ CM = 28° (at the lower energies) or θ CM = 18° (at the higher energies) to θ CM > 90°. The shape of the angular distribution A oono ( pp ) = ƒ(θ CM ) changes considerably with increasing energy. The new data show the onset of a characteristic t -dependence of the analyzing power, with a minimum at − t ≅ 1.0 (GeV/ c ) 2 followed by a second maximum at − t ≅ 1.5 (GeV/ c ) 2 . This structure is present at all energies, from kinematic threshold to 200 GeV.

Measurement of np and pp asymmetry with an accelerated polarized deuteron beam from 725 to 1000 MeV per nucleon

Abstract The accelerated polarized deuteron beam of Saturn II was used to measure the analyzing power for np elastic scattering at five energies. The left-right asymmetries e = (L + R)/(L + R) for np and for pp elastic scattering were measured simultaneously by CH2− carbon subtraction using one of the beam-line polarimeters. The analyzing power A00n0(np) is given by the ratio enpd/eppd multiplied by the known analyzing power for pp elastic scattering. Experimental evidence is consistent with the underlying assumption that in the kinetmatic region of the experiment the ratio of the np to pp analyzing powers for scattering of quasifree nucleons in deuterons is the same as for scattering of free neutrons and protons, respectively.