V. N. Matafonov

Observation of significant spin effects in hard collisions at 40 GeV/c

Abstract A single-spin asymmetry in the inclusive π 0 production at small x F was measured. In the experiment 40 GeV/c π − mesons were incident on transversely polarized protons and deutrons. An asymmetry of (40–50)% has been revealed in the hard scattering region.

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.

Proton and neutron polarized targets for nucleon-nucleon experiments at SATURNE II

Abstract A SATURNE polarized target has been used for nucleon-nucleon elastic scattering and transmission experiments for 15 years. Continuous improvements resulted in a flexible and reliable facility for spin physics. The polarized proton target was a 70 cm 3 cartridge loaded with pentanol-2, a promising material according to the results obtained. The new acquisition system and data processing was based on the LabView/PC software and increased the accuracy of polarization measurements. For a polarized neutron target, two cartridges loaded with 6 LiD and 6 LiH were set in the refrigerator and could be quickly inserted in the beam. Results from the the first experiments using 6 Li materials in quasielastic pp or pn analyzing power measurements are compared with the same observables measured in free nucleon-nucleon scattering using polarized proton targets. The angular resolution distributions for θ CM determination and azimuthal coplanarity are shown for different targets in nucleon-nucleon scattering. A comparison of analyzing power results for elastic and quasielastic scattering suggests that the contribution of inelastic processes to quasielastic pn scattering may be suppressed by additional constraints.

Frozen spin solid targets developed at the Laboratory of Nuclear Problems (JINR, Dubna)☆

Experience with polarized targets [1,2] and achieving of very low temperatures in 1966 at the Laboratory of Nuclear Problems [3] and by another group [4] gave rise to the idea of using a radically new technique based on dissolving 3He in 4He to create a frozen spin polarized target. The short history of the development of such proton and deuteron targets at the LNP is given. The complex Cr(V) compounds in diols are used as target operating material. A characteristic feature of these targets is a long relaxation time (∼ 1000h) in magnetic fields of about 0.5 T. Lately, the Saclay-Argonne frozen spin proton polarized target used initially in E704 experiment at FERMILAB has been upgraded with adding the missing parts and the first physics experiment has been carried out.

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.

The pp elastic scattering analyzing power measured with the polarized beam and the unpolarized target between 1.98 and 2.80 GeV

Abstract A polarized proton beam extracted from SATURNE II was scattered on an unpolarized CH2 target. The angular distribution of the beam analyzing power Aoono was measured at large angles from 1.98 to 2.8 GeV and at 0.80 GeV nominal beam kinetic energy. The same observable was determined at the fixed mean laboratory angle of 13.9° in the same energy range. Both measurements are by-products of an experiment measuring the spin correlation parameter Aoon.

Target with a frozen nuclear polarization for experiments at low energies

Abstract A target with a frozen spin polarization of protons in 1.2-propanediol with a paramagnetic Cr(V) impurity is described, intended for polarization parameter studies in np-scattering at approximately 15 MeV neutron energy. The target of cylindrical shape of 2 cm diameter and 6 cm long with an initial polarization of 95 ± 3%, obtainable by the dynamic polarization technique, is placed at a temperature about 20 mK in a magnetic field of 0.37 T generated by a magnetic system, which provides a large aperture for scattered particles. The relaxation time for the spin polarization in an experiment is about 1000 hours.

Frozen spin polarised deuteron target 60 cm3 in volume

A frozen spin polarised deuteron target cooled by a dilution refrigerator is described. Fully deuterated ethanediol and propanediol synthesised with a Cr(V) complex are used as the target materials. The following results are obtained: the maximum polarisation is 0.4, the maximum spin-lattice relaxation time is up to approximately 1500 h at 20 mK and 0.53 T.

Measurements of energy behaviour of spin-dependentnp—observables over 1.2–3.7 GeV energy region Dubna “Delta-Sigma” Experiment

New accurate data on the neutron-proton spin-dependent total cross section difference ΔσL(np) at the neutron beam kinetic energies 1.4, 1.7, 1.9 and 2.0 GeV are presented. A number of physical and methodical results on investigation of an elasticnp→pn charge exchange process over a few GeV region are also presented. Measurements were carried out at the Synchrophasotron and Nuclotron of the Veksler and Baldin Laboratory of High Energies of the Joint Institute for Nuclear Research.

Single-spin asymmetry of inclusive neutral-pion production in pp∩ interactions at 70 GeV in the region -0.4 < xf < -0.1

For the kinematical region specified by the inequalities −0.4 < xF < −0.1 and 0.9 < pT < 2.5 GeV/c, the results are presented that were obtained by experimentally determining the single-spin asymmetry of inclusive neutral-pion production in the reaction p + p↑ → π0 + X at 70 GeV. According to these results, the asymmetry is close to zero in the region −0.2 < xF < −0.1 and grows in magnitude with decreasing xF, amounting to (−10.6 ± 3.2)% for −0.4