Yu. A. Plis

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.

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.

Preparation of new polarization experiment SPASCHARM at IHEP

A new experiment SPASCHARM devoted to a systematic study of polarization phenomena in hadron-hadron interactions in the energy range 10-70 GeV is under preparation at IHEP (Protvino). The physical observables will be single-spin asymmetries, hyperon polarizations and spin-density matrix elements. A universal setup will detect and identify various neutral and charge particles in the full azimuthal angle and a wide polar angle range. A polarized target is used to measure the SSA. The SPASCHARM sub-detectors are being designed and constructed now. The possibility of obtaining a polarized proton beam for the SPASCHARM experiment from Lambda decays is under study.

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

Measurement of spin dependent total cross sections in neutron‐deuteron scattering

Since the beginning of nuclear physics, a central issue has been understanding the nucleon-nucleon (NN) force. Due to the progress in the development of new theoretical models as well as due to new experimental data our understanding of the NN system increased significantly during last 15 years. However, when these models were used to predict properties of three-nucleon (3N) system, they failed to provide a similarly exact picture.

Single-spin asymmetry of inclusive π0-meson production in 40-GeV pion interactions with a polarized target in the target-fragmentation region

Data on the single-spin asymmetry (AN) of inclusive π0 production in 40-GeV pion interactions with a polarized target, π−+↑→π0+X, are presented for the target-fragmentation region. The result is AN=(−13.8±3.8)% for −0.8<xF<−0.4 and 1<pT<2 GeV/c and is compatible with zero for −0.4<xF<−0.1 and 0.5<pT<1.5 GeV/c. At a π0 momentum of about 1.7 GeV/c in the c.m. frame, the asymmetry becomes nonzero both in the central and in the target-fragmentation region. The behavior of the asymmetry is similar to that observed in the beam-fragmentation region of the E-704 (FNAL, 200 GeV) and STAR (BNL, 20 TeV) experiments, which employed a polarized proton beam.

The new source of polarized ions for the JINR Accelerator Complex

The project assumes the design and construction of a universal high-intensity source of polarized deuterons (protons) using a charge-exchange plasma ionizer. The output ↑D+ (↑H+) current of the source is expected to be at a level of 10 mA. The polarization will be up to 90% of the maximal vector (±1) for ↑D+ (↑H+) and tensor (+1,−2) for ↑D+ polarization. Realization of the project is carried out in close cooperation with INR of RAS (Moscow). The equipment available from the CIPIOS ion source (IUCF, Bloomington, USA) is partially used for the Dubna device. The new source at the JINR NUCLOTRON accelerator facility will make it possible to increase the polarized deuteron beam intensity up to the level of 1010 d/pulse. Previous test runs on acceleration of polarized deuterons at the NUCLOTRON up to about 1 GeV/u and slow extraction of the beam to the beam transfer lines, have shown the absence of depolarization resonances. The first dangerous resonance is predicted at the beam energy of 5.6 GeV/u. The source could be transformed into a source of polarized negative ions if necessary.

Searches for single-spin asymmetry in the inclusive production of neutral pions in the central region at a proton beam energy of 70-GeV

Results are presented that were obtained by measuring single-spin asymmetry in the inclusive production of neutral pions in the reaction p+p ↑→ π0+X at xF≈0. A beam of 70-GeV protons was extracted directly from the vacuum chamber of the accelerator by means of a bent single crystal. For transverse momenta in the range 1.0<pT<3.0 GeV/c, the single-spin asymmetry independently measured by two detectors is zero within the errors. This result is in agreement with Fermilab data obtained at 200 GeV, but it is at odds with CERN data measured at 24 GeV.

Source of polarized ions and polarized beams at the NUCLOTRON

The paper describes the JINR polarized ion source operating by means of the atomic beam method. The results of testing of the plasma ionizer with a storage cell and tuning of high frequency transition units are presented. The source was installed in the linac injector hall of the NUCLOTRON in May 2016. The source was commissioned and used in the NUCLOTRON runs in 2016 and February – March 2017. Polarized and unpolarized deuteron beams as well as polarized proton beam were produced to accelerate in the NUCLOTRON. The polarized deuteron beam with pulsed current up to 3.7 mA has been produced. Deuteron beam polarization of 0.6-0.9 of theoretical values for different modes of high frequency transition units has been measured with the NUCLOTRON ring internal polarimeter for the accelerated deuteron and proton beams.