VBLHEP Specialised Seminar

A. M. Baldin Relativistic nuclear physics and polarisation phenomena #795

Date and Time: Wednesday, 26 January 2022, at 11:00 AM

Venue: VBLHEP Conference Hall (bld. 3), the Veksler and Baldin Laboratory of High Energy Physics

Seminar topic: “The measurements of spin-independent part of np→pn forward scattering at energies T_n = 0.55 ÷ 2.0 GeV”
“Delta-Sigma” experiment

Speaker: R. A. Shindin

Abstract:

According to the Pauli principle in the quasi-elastic nd→p(nn) reaction with proton scattering to the zero angle (at small momentum transfer q_nn=P_n‒P_p) two neutrons in the recoil can form only the S-wave state with full spin S_nn = 0, therefore during the charge-exchange of bound (deuteron) proton into the neutron its spin reverses also (Pomeranchuk-Chew hypothesis). Within the impulse approximation this process is determined by the spin-dependent amplitudes of elastic np→pn scattering. The measurement of the differential cross-sections of quasi-elastic nd→p(nn) and elastic np→pn reactions and determination the R_dp-ratio between them allows to extract the spin observables in experiments with unpolarized particles.

Similar experiments were carried out at energies T < 1 GeV in different times at laboratories LAMPF, LRL, UCRL, Harwell and so on. In the period 2002-07 using the accelerator complex Nuclotron LHE LINR was obtained new values of R_dp-ratio in the interval from 0.5 to 2 GeV. Experimental data was compared with the prediction of phase shift analysis (PSA) and good agreement was observed. Main results of performed work that the spin-dependent and spin-independent parts of the differential cross section for the charge-exchange reaction np→pn in the energy range T_n = 0.5 ÷ 2.0 GeV and proton scattering to the zero angle are about 85% and 15% respectively.

(On the sources of PhD thesis)

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