A. I. Kovalev

A movable polarized target for high energy spin physics experiments

A movable polarized target has a volume 140 cm3 (20 cm long and 3 cm diameter). Polarizing magnet was tested to 6.5T, homogeneity is better than 2 × 10−4. The nuclear spin relaxation time in a frozen mode (at a temperature 50 mK and magnetic field 2.5T) is over 1000 h. Maximum values of proton polarization obtained were 80% and 85% for positive and negative polarization, respectively.

Measurements of spin rotation parameter A in pion proton elastic scattering at 1.62-GeV/c

Abstract The ITEP-PNPI Collaboration presents the results of the measurements of the spin rotation parameter A in the elastic scattering of positive and negative pions on protons at Pbeam=1.62 GeV/c. The setup included a longitudinally-polarized proton target with superconductive magnet, multiwire spark chambers and a carbon polarimeter with thick filter. Results are compared with the predictions of partial wave analyses. The experiment was performed at the ITEP proton synchrotron, Moscow.

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.

Measurement of the spin rotation parameter A+ in the elastic scattering of positive pions on a longitudinally-polarized proton target in the second resonance region

Abstract The ITEP-PNPI collaboration presents the first results of the spin rotation parameter A+ measurements in the second resonance region. The experiment was performed at the ITEP accelerator at a positive pion beam momentum 1.43 GeV/c for scattering angles θcm = 127° and 133°. The setup was based on a polarized proton target and a carbon-plate polarimeter. The obtained data is compared with the predictions of the existing partial-wave analyses.

Polarization in quasielastic (p, 2p) scattering on a 4He nucleus at 1 GeV

The polarization of secondary protons from the (p, 2p) reaction induced by 1-GeV protons incident to a 4He nucleus was measured in a kinematically complete experiment. By using a two-arm magnetic spectrometer, two secondary protons from this reaction were recorded in coincidence at unequal scattering angles of Θ1 = 18°−24.21° and Θ2 = 53.22° over a broad range of the recoil-nucleus momentum KB between 0 and 150 MeV/c. It was found that the measured polarization of either secondary proton is less than that observed in free elastic proton-proton scattering. The magnitude of this difference is determined by the mean binding energy of s-shell protons rather than by the effective nuclear density. The polarizations measured in inclusive quasielastic and elastic scattering of 1-GeV protons on 4He nuclei are presented for scattering angles in the range Θ1 = 18° − 24.21°.

Backward asymmetry measurements in the elastic pion-proton scattering at resonance energies

The asymmetry parameter P was measured for the elastic pion-proton scattering in the very backward angular region of

Measurement of the spin rotation parameter Ain the elastic pion-proton scattering at 1.43 GeV/c

\theta_{{\rm CM}}^{}

Energy dependence of the spin-spin correlation parameter CNN at 50° and 90° c.m. for pp-elastic scattering in the energy range 0.69–0.95 GeV

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Measurement of the Polarization Parameter P in π-p Elastic Scattering in the Energy Range 450–600 MeV

150 - 170° at several pion beam energies in the invariant-mass range containing most of the pion-proton resonances. The general goal of the experimental program was to provide new data for partial wave analyses in order to resolve their uncertainties in the baryon resonance region to allow the unambiguous baryon spectrum reconstructions. Until recently the parameter P was not measured in the examined domain that might be explained by the extremely low cross-section. At the same time the predictions of various partial wave analyses are far from agreement in some kinematic areas and specifically those areas were chosen for the measurements where the disagreement is most pronouncing. The experiment was performed at the ITEP U-10 proton synchrotron, Moscow, by the ITEP-PNPI Collaboration in the latest 5 years.