Nucleon-Nuclei Interactions Group

    The group was found in 1966, and initially had name “Nucleon-Nucleon Interaction Group”. In 1981 the group was converted into the sector with the same name. From 1986 to 2002 the division had name “Polarization Phenomena Laboratory”. Because the main direction of investigations was changed, in 2003 the laboratory was transformed into the “Nucleon-Nuclei Interactions Group”.
    Early on the group experimentally studied the elastic and inelastic processes in nucleon-nucleon interaction. In an experiment “Study of p ⁺ - Meson Production in pp ® p ⁺pn Reaction at 1000 MeV” were measured the momentum spectra of p ⁺mesons in the wide angular range from 30.5° to 125° c.m. angles. The experimental data were satisfactory fitted to the OPE-model predictions including the Legendre polynomials P₂(cosQ _o) and P₄(cosQ _o).
    Within the program of nucleon-nucleon interaction study, the group designed the general-purpose system for creation and transporting the polarized proton beam. Protons were polarized in the scattering of an external beam on a fixed solid-state target. To optimize the experimental condition, there were measured the proton polarization in scattering at nuclei Be, C, Al, and Pb in the range 3° – 12° l.s. at 1000 MeV. The system allowed to polarize the beam in horizontal, vertical, and longitudinal directions and inverse the chosen polarization direction.
    The group designed installation and developed the method of measurement polarization parameters. Firs in the world was measured the carbon analyzing power A_pC at energies 640 – 1000 MeV.
    At energy 970 MeV first were measured triple-scattering polarization parameters D(D_t), R,(R_t), A(A_t) in the range 30° – 90° c.m. New measurements were used in the phase-shift analysis of the pp-scattering.
    The usage of the Frozen Spin Polarized Target (FSPT) starts the new phase of investigation the nucleon-nucleon scattering. The FSPT was designed at JINR (Dubna) and had one of the best polarization value and relaxation time in the world. With help of the FSPT were measured:

Polarization correlation parameter C_nn(90°) at 600 – 950 MeV;
Energy and angular dependence of the parameter A_nn(C_nn) in the arge
700 – 950 MeV;
Energy and angular dependence of the parameter K_nn(D_t) at energies
800, 850, 900, 950 MeV;
Vector polarization in the reaction p⁺d®pp;
Polarization transfer parameter K_nn at low angles 9°-16° c.m. (22-40° l.s).

Since 1998, using newly created proton beam with varying energy from 200 to 1000 MeV, were measured proton induced fission cross-sections at nuclei ²⁰⁹Bi, ²³²Th, ^233,235,238U, ²³⁷Np, ²³⁹Pu. This work was performed together with the Accelerator team and was sponsored by International Scientific-Technical Center.