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Register a new userIn-medium nucleon dynamics at short range: ground-state energy,radii, momentum distribution and spectral functions of few-nucleon systems and complex nuclei
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Talk given at the International Workshop on (e,ep) Processes, July 2-6, 2017, Bled, Slovenia. Various many-body calculations are compared and the results provided by the Normalization Conserving Linked Cluster Expansion with realistic NN interactions are reviewed and analyzed in detail, as far as ground state energies, momentum distributions and spectral functions of few-nucleon system and complex nuclei are concerned.
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Using realistic wave functions, the proton-neutron and proton-proton momentum distributions in $^3He$ and $^4He$ are calculated as a function of the relative, $k_{rel}$, and center of mass, $K_{CM}$, momenta, and the angle between them. For large values of ${k}_{rel}gtrsim 2,,fm^{-1}$ and small values of ${K}_{CM} lesssim 1.0,,fm^{-1}$, both distributions are angle independent and decrease with increasing $K_{CM}$, with the $pn$ distribution factorizing into the deuteron momentum distribution times a rapidly decreasing function of $K_{CM}$, in agreement with the two-nucleon (2N) short range correlation (SRC) picture. When $K_{CM}$ and $k_{rel}$ are both large, the distributions exhibit a strong angle dependence, which is evidence of three-nucleon (3N) SRC. The predicted center-of-mass and angular dependence of 2N and 3N SRC should be observable in two-nucleon knock-out processes $A(e,epN)X$.
By analyzing recent microscopic many-body calculations of few-nucleon systems and complex nuclei performed by different groups in terms of realistic nucleon-nucleon (NN) interactions, it is shown that NN short-range correlations (SRCs) have a universal character, in that the correlation hole that they produce in nuclei appears to be almost A-independent and similar to the correlation hole in the deuteron. The correlation hole creates high-momentum components, missing in a mean-field (MF) description and exhibiting several scaling properties and a peculiar spin-isospin structure. In particular, the momentum distribution of a pair of nucleons in spin-isospin state $(ST)=(10)$, depending upon the pair relative ($k_{rel}$) and center-of-mass (c.m.) ($K_{c.m.}$) momenta, as well as upon the angle $Theta$ between them, exhibits a remarkable property: in the region $k_{rel}gtrsim 2,fm^{-1}$ and $K_{c.m.}lesssim 1,fm^{-1} $, the relative and c.m. motions are decoupled and the two-nucleon momentum distribution factorizes into the deuteron momentum distribution and an A-dependent momentum distribution describing the c.m. motion of the pair in the medium. The impact of these and other properties of one- and two-nucleon momentum distributions on various nuclear phenomena, on ab initio calculations in terms of low-momentum interactions, as well as on ongoing experimental investigations of SRCs, are briefly commented.
Universality of short range correlations has been investigated both in coordinate and in momentum space, by means of one-and two-body densities and momentum distributions. In this contribution we discuss one- and two-body momentum distributions across a wide range of nuclei and their common features which can be ascribed to the presence of short range correlations. Calculations for few-body nuclei, namely 3He and 4He, have been performed using exact wave functions obtained with Argonne nucleon-nucleon interactions, while the linked cluster expansion technique is used for medium-heavy nuclei. The center of mass motion of a nucleon-nucleon pair in the nucleus, embedded in the full two-body momentum distribution n_NN(krel,KCM), is shown to exhibit the universal behavior predicted by the two-nucleon correlation model, in which the nucleon-nucleon pair moves inside the nucleus as a deuteron in a mean-field. Moreover, the deuteron-like spin-isospin (ST)=(10) contribution to the pn two-body momentum distribution is obtained, and shown to exactly scale to the deuteron momentum distribution. Universality of correlations in two-body distributions is cast onto the one-body distribution n(k1), obtained by integration of the two-body n_NN(k1, k2): in particular, the high momentum part of n(k1) exhibits the same pattern for all considered nuclei, in favor of a universal character of the short range structure of the nuclear wave function. Perspectives of this work, namely the calculation of reactions involving light and complex nuclei with realistic wave functions and effects of Final State Interactions (FSI), investigated by means of distorted momentum distributions within the Glauber multiple scattering approach, are eventually discussed.
We present a preliminary calculation of the electromagnetic form factors of $^3$He and $^3$H, performed within the Light-Front Hamiltonian Dynamics. Relativistic effects show their relevance even at the static limit, increasing at higher values of momentum transfer, as expected.
The interpretation of recent Jlab experimental data on the exclusive process A(e,ep)B off few-nucleon systems are analyzed in terms of realistic nuclear wave functions and Glauber multiple scattering theory, both in its original form and within a generalized eikonal approximation. The relevance of the exclusive process 4He(e,ep)^3H for possible investigations of QCD effects is illustrated.
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