M. de Mali

Energy dependence of the neutron-proton total cross section differences ΔσT and ΔσL between 0.31 and 1.1 GeV

Abstract Final results for total cross section differences ΔσT and ΔσL measured with a polarized neutron beam transmitted through a polarized proton target are presented. Measurements were carried out at SATURNE II, at 11 energies between 0.63 and 1.1 GeV for ΔσT and at 9 energies between 0.312 and 1.1 GeV for ΔσL. The results are compared with measurements at PSI and LAMPF as well as with ΔσL data points deduced from p-d and p-p transmission experiments at the ANL-ZGS. The present results together with the corresponding pp data allow to determine two of the three imaginary parts of forward scattering amplitudes for isospin I = 0.

Apparatus for the measurement of spin dependent observables in np and pp elastic and quasi-elastic scattering

Abstract The present article describes an apparatus used for the measurement of spin dependent observables at SATURNE II. Observables for np elastic and quasi-elastic scattering were measured between 0.31 and 1.1 GeV, those for pp elastic scattering between 1.94 and 2.24 GeV. Measurements of pn and pp observables with an unpolarized 6LiD and 7LiH targets around 2 GeV were also carried out. Fast electronics, on-line data acquisition, event selection and off-line analysis are presented.

Angular dependence of analyzing power in np elastic scattering between 0.312 and 1.10 GeV

Abstract We present a total of 427 np analyzing power data points in a large angular interval at 12 energies between 0.312 and 1.10 GeV. The SATURNE II polarized beam of free monochromatic neutrons was scattered either on the Saclay frozen-spin polarized proton target or on CH2 and C targets. Present results are compared with existing elastic and quasieleastic data.

Measurement of the spin dependent neutron-proton total cross section differences ΔσT and ΔσL between 0.63 and 1.08 GeV

Abstract We present first measurements of total cross section differences Δσ T and Δσ L for a polarized neutron beam transmitted through a polarized proton target. Measurements were carried out at SATURNE II, at 0.63, 0.88, 0.98 and 1.08 GeV. The results are compared with Δσ L data points deduced from p-d and p-p transmission experiments, and with phase shift analyses predictions. The present results together with the corresponding pp data yield two of the three spin dependent forward scattering amplitudes for isospin I =0.

Observation of a narrow structure in the pp elastic scattering observable Aoonn at Tkin=2.11 GeV

Abstract The angular dependece of the pp elastic scattering spin correlation parameter was measured in the angular range from 60° to 97° CM at 14 energies between 1.96 and 2.23 GeV. A rapid decrease of the energy dependence of this observable at 90° CM is observed around 2.11 GeV kinetic energy. This agrees with the behavior of A oonn predicted on the basis of an exotic six-quark structure. The A oonn (90° CM ), together with the known differential cross section, allows the determination of the absolute value of the pure spin-singlet amplitude. The energy dependence of this amplitude shows a shoulder centered at 2.11 GeV, corresponding to a total mass of 2.735 GeV and an estimated width of 17 MeV.

Angular dependence of the beam and target analyzing powers Aoono and Aooon in np elastic scattering between 0.477 and 0.940 GeV

Abstract We present a total of 273 independent data points of the analyzing powers A oono (nP) and A ooon (nP) in a large angular interval at four energies between 0.477 and 0.940 GeV. The SATURNE II polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the polarized Saclay frozen-spin proton target. Part of the data was obtained with a CH 2 target. A comparison of the two measured observables allows one to determine the polarization of the neutron beam. The present results provide an important contribution to any future theoretical or phenomenological analysis.

Angular dependence of the spin correlation parameter Aoonn in np elastic scattering between 0.8 and 1.1 GeV

Abstract We present a total of 323 data points of the spin correlation parameter A oonn (np) in a large angular interval at eight energies between 0.8 and 1.1 GeV. The SATURNE II polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the polarized Saclay frozen-spin proton target. The present data are the first existing results above 0.8 GeV.

Measurement of the spin correlationA ookk innp elastic scattering between 0.63 and 1.08 GeV

We present the measurements of the spin correlation parameterAookk(np). A longitudinally polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the longitudinally polarized Saclay frozen-spin proton target. Measurements were carried out at SATURNE II, at neutron beam kinetic energies of 0.63, 0.88, 0.98 and 1.08 GeV. The data points cover the angular region from about 40° to 110° CM. The observed angular dependence ofAookk(np) at 0.63 GeV agree with the phase shift analysis predictions except at small angles.

Measurement at SATURNE, with a free polarized neutron beam, of cross sections and spin observables for the neutron-proton system

Abstract Experiments currently done at SATURNE (Saclay) with a free polarized neutron beam are described. These are measurements for the np system of elastic and inelastic cross sections and analysing powers, and of Δσ T and Δσ L .

Angular dependence of pp spin correlation and rescattering observables between 1.80 and 2.10 GeV

A polarized proton beam extracted from SATURNE II and the Saclay polarized proton target were used to determine the spin correlation parameter Aoosk and the rescattering observablesKos″ so; Dos″ok, Nos″sn, andNonsk at 1.80 and 2.10 GeV. The beam polarization was oriented perpendicular to the beam direction in the horizontal scattering plane and the target polarization was directed either along the vertical axis or longitudinally. Left-right and up-down asymmetries in the second scattering were measured. A check for the beam optimization with the beam and target polarizations oriented vertically provided other observables, of which results forDonon andKonno at 1.80, 1.85, 2.04, and 2.10 GeV are listed here. The new data at 2.10 GeV suggest a smooth energy dependence of spin triplet scattering amplitudes at fixed angles in the vicinity of this energy.