The 24th International Spin Symposium

Contribution ID: 119

Type: Parallel Session Presentation

POLARIZATION TEST FOR QUASI-FREE
KNOCKOUT OF NUCLEON FROM NUCLEAR
SHORT-RANGE CORRELATED NN PAIR
Monday, 18 October 2021 21:30 (20 minutes)
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 12 C+p 10 A+pp+N was studied at BM@N
in JINR [2] using the 12 C beam at energy of 4 GeV/nucleon interacting with the hydrogen target to probe theSRC pairs {pN} in the 12 C. The pp scattering in the subprocess p+{pN} p+p+N occured at the scattering angles~ 90° in the pp c.m.s. and all three final nucleons were detected as well as the residual nucleus 10 A. For theoretical analysis of this reaction [3] is used a properly modified approach developed earlier [4] to describe thequasi-elastic knock-out of fast deuterons from the light nuclei 12 C and 7,6 Li by protons in the reactions (p,pd)
and (p,nd). A basic assumption in theoretical description of SRC NN correlations in nuclei is a factorizationof the two-nucleon momentum distribution in nucleus n(k1 , k2 ) over the internal, nrel (qrel ), and the c.m.s.,ncm (kc.m. ), momenta [1]. For the internal nrel (qrel ) distribution the deuteron (or singlet deuteron) wave
function squared is used for the realistic NN-interaction potentials. Relativistic effects in the quasi-elastic
knockout of nucleon from the SRC pair p+{NN} p+N+N are taken into account in the light-front dynamics[5] similarly to the deuteron breakup reaction p+d p+p+n. According to the results of the data analysis of the12C+p 10 A+ pp+N reaction [2] the initial and final state interaction (ISI&FSI) with nuclear medium is nonimportant in the reaction in question at kinematic conditions of the BM@N experiment. Here we estimatedthe ISI&FSI effects within the eikonal approximation using the Glauber model for the N-10 A scattering. The
one-loop approximation with elastic N-10 A rescatterings was applied and the ISI&FSI effect was found to bemoderate. However, another question concerning the mechanism of the subprocess p+{NN} p+N+N and therole of ISI&FSI in it is much less clear. Only in case of dominance of the quasi-free mechanism (or impulseapproximation) of the nucleon knockout in the subprocess p+{NN} p+N+N one can extract the internal momentum distribution nrel (qrel ) from the data on the reaction 12 C+p 10 A+ pp+N. One can show (see Ref. [6]and references therein), that the tensor analyzing power T20 of the reaction p+d p+p+n for the quasi-freemechanism of the nucleon is easily expressed via the ratio u(q)/w(q) of the S- and D- components of thedeuteron wave function in the momentum space u(q) and w(q), respectively, and has a very specific behavior
as a function of the module of q [6]. Therefore, a measurement of the T20 in the reaction p+d p+p+n at thesame kinematics as for the subprocess p+{NN} p+N+N in the reaction A(p,ppN)B, i. e. at large momentumof the nucleon spectator and large pp-scattering angle ~ 90°, and a subsequent comparison with the results of
the IA calculation of the T20 , will provide a crucial test for the quasi-free mechanism of this subprocess. A
similar test based on the measurement of the T20 of the reaction e+d e+p+n can be used to check quasi-freemechanism of the nucleon knockout by electron from the SRC NN pair in the reaction A(e,epN)B.
This work is supported in part by the RFBR grant № 18-02-40046.
1. O. Hen et al., Rev. Mod. Phys. 89 (2017) 045002.
2. M. Patsyuk et al. Nature Phys. 17 (2021) 693; arXiv:2102.02626 [nucl-ex].
3. Yu.N. Uzikov, Izv. RAN, Ser. Fiz. 84 (2020) 580.
4. M.A. Zhusupov, Yu.N. Uzikov, Fiz. El. Chast. At. Yadr. 18 (1987) 323.
5. Yu.N. Uzikov, EPJ Web Conf, 222 (2019) 03027.
6. S.L. Belostotski et al., Phys. Rev. C 56 (1997) 50.

Primary author: UZIKOV, Yuriy (Joint Institute for Nuclear Researches, DLNP)

Presenter: UZIKOV, Yuriy (Joint Institute for Nuclear Researches, DLNP)
Session Classification: Spin in Nuclear Reactions and Nuclei
Track Classification: Parallel Sessions: Spin in Nuclear Reactions and Nuclei