Chiara Benedetta Mezzetti

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

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 Schrodinger 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.

UNIVERSALITY OF NUCLEON NUCLEON SHORT-RANGE CORRELATIONS AND NUCLEON MOMENTUM DISTRIBUTIONS

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 (krel) and center-of-mass (c.m.) (Kc.m.) momenta, as well as upon the angle Θ between them, exhibits a remarkable property: in the region krel≳2 fm-1 and Kc.m.≲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.

Microscopic nucleon spectral function for finite nuclei featuring two- and three-nucleon short-range correlations: The model versus ab initio calculations for three-nucleon systems

The main features of the convolution model which, in the region of two-nucleon (2N) and three-nucleon (3N) short-range correlations (SRC), describes the one-nucleon momentum distribution n(k_1) and the spectral function P(k_1,E) in terms of a convolution integral involving the relative n_{rel}(k_{rel}) and the center-of-mass n_{c.m.}(K_{c.m.}) momentum distributions of a nucleon-nucleon pair, are illustrated in detail. It is stressed that the model, which stems from the universal property of factorization exhibited by the nuclear wave function at short inter-nucleon distances, is only applicable in a well-defined region of k_{rel} and K_{c.m.}; it is shown, in particular, that the requirement of factorization introduces a severe constraint on the values of k_{rel} and K_{c.m.} that appear in the convolution integral. Using ab-initio relative and c.m. momentum distributions for ^3He, the validity of the convolution model is investigated by comparing the model spectral function and momentum distributions with the ones resulting from ab-initio calculations performed with realistic local NN interaction of the Argonne family. It is shown that when the constraint on the value of k_{rel} and K_{c.m.} are correctly taken into account and only 2N SRC are taken into account, the convolution model is in good agreement with the ab-initio spectral function in the region of the peak exhibited by the latter, whereas far from the peak, particularly at high values of the removal energy, the model spectral function can be qualitatively reconciled with the ab-initio spectral function only by considering the effects of 3N SRC. As for the nucleon momentum distribution, the effects of 3N SRC appears to be very small.

Number of collisions in the Glauber model and beyond

The so-called number of hadron-nucleus collisions n{sub coll}(b) at impact parameter b and its integral value N{sub coll}, which are used to normalize the measured fractional cross section of a hard process, are calculated within the Glauber-Gribov theory, including the effects of nucleon short-range correlations. The Gribov inelastic shadowing corrections are summed to all orders by employing the dipole representation. Numerical calculations are performed at the energies of the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC). We found that whereas the Gribov corrections generally increase the value of N{sub coll}, the inclusion of nucleon correlations, acting in the opposite directions, decreases it by a comparable amount. The interplay of the two effects varies with the value of the impact parameter.

Obtaining information on short range correlations from inclusive electron scattering

In view of recent data from the Thomas Jefferson National Accelerator Facility (JLab) on inclusive electron scattering off nuclei at high momentum transfer

Short Range Correlations in Medium‐ and High‐Energy Scattering off Nuclei

({Q}^{2}\ensuremath{\gtrsim}1 {\mathrm{GeV}}^{2})

Universality of nucleon-nucleon short-range correlations: two-nucleon momentum distributions in few-body systems

and their current analysis, it is shown that, if the scaling variable is properly chosen, the analysis in terms of scaling functions can provide useful information on short-range correlations (SRC). This is demonstrated by introducing a new relativistic scaling variable that incorporates the momentum dependence of the excitation energy of the

Slow-proton production in semi-inclusive deep inelastic scattering off the deuteron and complex nuclei: Hadronization and final-state interaction effects

(A\ensuremath{-}1)

A novel analysis of the effects of short range correlations in inclusive lepton scattering off nuclei

system, with the resulting scaling function being closely related to the longitudinal momentum distributions.

Tagging emc effects and hadronization mechanisms by semi-inclusive deep inelastic scattering off nuclei

The effects of short range correlations in lepton and hadron scattering off nuclei at medium and high energies are discussed.