ИСТИНА

Short-range correlated (SRC) NN pairs play an important role in structure of atomic nuclei and are actively studied using electron and proton beams [1]. Recently the reaction 12C+p→10A+pp+N was studied at BM@N in JINR [2]using the 12C beam at energy of 4 GeV/nucleon in inverse kinematics providing interaction with the hydrogen target to probe the SRC pairs in the 12C. The pp scattering occurs at ~ 90° in c.m.s. of the pp and all three nucleons are detected in the final state as well as the residual nucleus 10A. For theoretical analysis [3] of this reaction a properly modified approach is used developed earlier (see Ref. [4] and references therein) to describe the quasi-elastic knock-out of fast deuterons from the light nuclei 12C and 7,6Li by protons in the reactions (p,pd) and (p,nd) at the proton beam energy 670 MeV [5]. Elementary sub-processes in the (p,Nd) reactions were the backward quasi-elastic scattering of the proton on the two-nucleon clusters p{pn}→pd and p{nn}→nd. A basic assumption in theoretical description of SRC NN correlations is factorization of the two-nucleon momentum distribution in nucleus n(k1,k2) over the internal nrel (qrel) and the c.m.s. ncm (kc.m.) momenta. For the internal nrel (qrel) distribution the deuteron (or singlet deuteron) wave function squared for the realistic potentials of NN-interaction potential is used. Relativistic effects in the sub-process p+{NN}➛p+N+N of quasi-elastic knockout of nucleon from the SRC pair are taken into account in the light-front dynamics [6] similarly to the deuteron breakup reaction p+d→p+p+n. According to the results of the data analysis of the 12C+p→10A+ pp+N reaction [2] the initial and final state interaction (ISI&FSI) with nuclear medium are negligible in the reaction in question at kinematic conditions of this experiment. The ISI&FSI effects are estimated here within the eikonal approximation using the Glauber model for the N-10A scattering. The one-loop approximation with elastic N-10A rescatterings is applied and the ISI&FSI effect is also found to be moderate. However another question concerning the mechanism of the sub-process p+{NN}➛p+N+N and the ISI&FSI in it is much less clear. Only in case of the quasi-free mechanism of nucleon knockout (or impulse approximation) dominates in the sub-process p+{NN}➛p+N+N one indeed can extract the internal momentum distribution nrel (qrel) from the data on the reaction 12C+p→10A+ pp+N. One can show, that for the quasi-free mechanism of the nucleon knockout in the reaction p+d→p+p+n the tensor analyzing power T20 in this reaction is easily expressed via the ratio of the S- and D- components of the deuteron wave function in the momentum space u(qrel ) and w(qrel ), respectively, and has a very specific behavior as a function of the module of qrel . Therefore, measurement of the T20 in the reaction p+d→p+p+n at the same kinematics as in the sub-process p+{NN}➛p+N+N of the reaction A(p,ppN)B, i. e. at large momentum of the nucleon spectator and large pp-scattering angle ~ 90°, and a subsequent comparison with the results of calculation of the T20 within the IA will provide a crucial test of the mechanism of this sub-process. A similar polarization test based on the measurement of the T20 of the reaction e+d→ e+p+n can be used to check quasi-free mechanism of nucleon knockout by electron from the SRC NN pair in the reaction A(e,epN)B.