Nucleon momentum distributions, their spin-isospin dependence, and short-range correlations

Alvioli M.(1,2), Ciofi degli Atti C.(3), Kaptari L.(4), Mezzetti C.(3), Morita H.(5), 2013, Nucleon momentum distributions, their spin-isospin dependence, and short-range correlations, Physical review. C. Nuclear physics (Print) 87 (2013): 034603-1–034603-19. doi_10.1103/PhysRevC.87.034603,

The nucleon momentum distribution nA(k) for A=2, 3, 4, 16, and 40 nuclei is systematically analyzed in terms of wave functions resulting from advanced solutions of the nonrelativistic Schrödinger equation, obtained within different many-body approaches based upon different realistic bare nucleon-nucleon (NN) interactions featuring similar short-range repulsion and tensor interactions. Particular attention is paid to the separation of the momentum distributions into the mean-field and short-range correlation (SRC) contributions. It is shown that although at high values of the momentum k different approaches lead to some quantitative differences, these do not hinder the general conclusion that the high-momentum behavior (k?1.5-2 fm-1) of all nuclei considered are very similar, exhibiting the well-known scaling behavior with the mass number A, independently of the used many-body approach and the details of the bare NN interaction. To analyze and understand the frequently addressed question concerning the relationships between the nucleus, nA(k), and the deuteron, nD(k), momentum distributions, the spin (S)-isospin (T) structure of few-nucleon systems and complex nuclei is analyzed in terms of realistic NN interactions and many-body approaches. To this end, the number of NN pairs in a given (ST) state, viz., (ST)=(10), (00), (01), and (11), and the contribution of these states to the nucleon momentum distributions are calculated. It is shown that, apart from the (00) state, which has very small effects, all other spin-isospin states contribute to the momentum distribution in a wide range of momenta. It is shown that for all nuclei considered the momentum distributions in the states T=0 and T=1 exhibit at k?1.5-2 fm-1 very similar behaviors, which represents strong evidence of the A-independent character of SRCs. The ratio nA(k)/nD(k) is analyzed in detail, stressing that in the SRC region it always increases with the momentum and the origin of such an increase is discussed and elucidated. The relationships between the one- and two-body momentum distributions, considered in a previous paper, are discussed and clarified, pointing out the relevant role played by the center-of-mass motion of a correlated pair in the (10) state. Eventually, the values of the the probability of high-momentum components in nuclei and the per nucleon probability a2 of deuteronlike configurations in nuclei are calculated, and the relationship of the present approach with the many-body methods based upon low-momentum effective interactions is briefly discussed.

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