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In light of the recent Jefferson Laboratory (JLab) data for the nuclear 12 C (e , e ′ p) transparencies, calculations, obtained in a relativistic multiple scattering Glauber approximation, are discussed. The shell-separated 12 C transparencies are shown and it is concluded that the p-shell nucleons are 75% more transparent than the s-shell ones. The presented comparisons between the calculations made here and the current 12 C (e , e ′ p) data show no clear indication for the onset of color transparency when implemented within the color diffusion model with standard parameters. [ABSTRACT FROM AUTHOR]

We provide a systematic study of the isospin composition and neutron-to-proton (N Z) ratio dependence of nuclear short-range correlations (SRC) across the nuclear mass table. We use the low-order correlation operator approximation (LCA) to compute the SRC contribution to the single-nucleon momentum distributions for 14 different nuclei from A = 4 to A = 208. Ten asymmetric nuclei are included for which the neutrons outnumber the protons by a factor of up to 1.54. The computed momentum distributions are used to extract the pair composition of the SRC. We find that there is a comprehensive picture for the isospin composition of SRC and their evolution with nucleon momentum. We also compute the non-relativistic kinetic energy of neutrons and protons and its evolution with nuclear mass A and N Z. Confirming the conclusions from alternate studies it is shown that the minority species (protons) become increasingly more short-range correlated as the neutron-to-proton ratio increases. We forge connections between measured nucleon-knockout quantities sensitive to SRC and single-nucleon momentum distributions. It is shown that the LCA can account for the observed trends in the data, like the fact that in neutron-rich nuclei the protons are responsible for an unexpectedly large fraction of the high-momentum components. [ABSTRACT FROM AUTHOR]

Short-range correlations (SRC) in asymmetric nuclei with an unusual neutron-to-proton ratio can be studied with quasi-free two-nucleon knockout processes following the collision between accelerated ions and a proton target. We derive an approximate factorized cross section for those SRC-driven p ( A , p ′ N 1 N 2 ) reactions. Our reaction model hinges on the factorization properties of SRC-driven A ( e , e ′ N 1 N 2 ) reactions for which strong indications are found in theory-experiment comparisons. In order to put our model to the test we compare its predictions with results of C 12 ( p , p ′ p n ) measurements conducted at Brookhaven National Laboratory (BNL) and find a fair agreement. The model can also reproduce characteristic features of SRC-driven two-nucleon knockout reactions, like back-to-back emission of the correlated nucleons. We study the asymmetry dependence of nuclear SRC by providing predictions for the ratio of proton–proton to proton–neutron knockout cross sections for the carbon isotopes 9−15 C thereby covering neutron excess values ( N − Z ) / Z between −0.5 and +0.5. [ABSTRACT FROM AUTHOR]

Background: Above the nucleon resonance region, the N(e,e'π±)N' data cannot be explained by conventional hadronic models. For example, the observed magnitude of the transverse cross section is significantly underestimated in a framework with Reggeized background amplitudes. Purpose: Develop a phenomenological framework for the N(e,e'π±)N' reaction at high invariant mass W and deep photon virtuality Q². Method: Building on the work of Kaskulov and Mosel [Phys. Rev. C 81, 045202 (2010)], a gauged pion-exchange current is introduced with a running cutoff energy for the proton electromagnetic transition form factor. A new transition form factor is proposed. It respects the correct on-shell limit, has a simple physical interpretation, and reduces the number of free parameters by one. Results: A study of the W dependence of the N(e,e'π±)N' lends support for the newly proposed transition form factor. In addition, an improved description of the separated and unseparated cross sections at -t ≤ 0.5GeV² is obtained. The predictions overshoot the measured unseparated cross sections for -t > 0.5GeV². Introducing a strong hadronic form factor in the Reggeized background amplitudes brings the calculations considerably closer to the high -t data. Conclusions: Hadronic models corrected for resonance-parton duality describe the separated pion electroproduction cross sections above the resonance region reasonably well at low -t. In order to validate the applicability of these models at high -t, separated cross sections are needed. These are expected to provide a more profound insight into the relevant reaction mechanisms. [ABSTRACT FROM AUTHOR]

Background: Short-range correlations (SRC) are an important ingredient of the dynamics of nuclei. Purpose: An approximate method to quantify the magnitude of the two-nucleon (2N) and three-nucleon (3N) short-range correlations and their mass dependence is proposed. Method: The proposed method relies on the concept of the "universality" or "local nuclear character" of the SRC. We quantify the SRC by computing the number of independent-particle model (IPM) nucléon pairs and triples which reveal beyond-mean-field behavior. It is argued that those can be identified by counting the number of nucléon pairs and triples in a zero relative orbital momentum state. A method to determine the quantum numbers of pairs and triples in an arbitrary mean-field basis is outlined. Results: The mass dependence of the 2N and 3N SRC is studied. The predictions are compared to measurements. This includes the ratio of the inclusive inelastic electron scattering cross sections of nuclei to ²H and ³He at large values of the Bjorken variable. Corrections stemming from the center-of-mass motion of the pairs are estimated. Conclusions: We find that the relative probability per nucléon for 2N and 3N SRC has a soft dependence with mass number A and that the proton-neutron 2N SRC outnumber the proton-proton (neutron-neutron) 2N SRC. A linear relationship between the magnitude of the EMC effect and the predicted number of proton-neutron SRC pairs is observed. This provides support for the role of local nuclear dynamics on the EMC effect. [ABSTRACT FROM AUTHOR]

Background: High-momentum nucleons in a nuclear environment can be associated with short-range correlations (SRC) that primarily occur between nucleon pairs. Observations and theoretical developments have indicated that the SRC properties can be captured by general quantitative principles that are subject to model dependence upon quantification. The variations in the aggregated effect of SRC across nuclei, however, can be quantified in an approximately model-independent fashion in terms of the so-called SRC scaling factors that capture the aggregated effect of SRC for a specific nucleus A relative to the deuteron (A-to-d). Purpose: We aim to provide predictions for the SRC scaling factors across the nuclear periodic table and determine the relative contribution of the different nucleon pair combinations to this quantity. We will also determine the SRC scaling factors for both bound protons and bound neutrons and study how these quantities evolve with the neutron-to-proton (N/Z) ratio in asymmetric nuclei. Methods: We employ the low-order correlation operator approximation (LCA) to compute the SRC contribution to the single-nucleon momentum distribution and ratios of A-to-d momentum distributions. We do this for a sample of fifteen nuclei from He to Pb, thereby gaining access to the evolution of the SRC scaling factor with the nuclear mass 4≤A≤208 and the neutron-to-proton ratio 1.0≤N/Z≤1.54. Results: We provide evidence for approximate A-to-d scaling of the single-nucleon momentum distribution at nucleon momenta exceeding about 4fm-1. For the studied sample of fifteen nuclei, the total SRC scaling factor is in the range 4.05-5.14, of which roughly 3 can be attributed to proton-neutron (pn) correlations. The SRC scaling factors receive sizable contributions from pp and nn correlations. They depend on the (N/Z) ratio reflecting the fact that the minority species (protons) becomes increasingly more short-range correlated with increasing (N/Z). We compare the computed SRC scaling factors in the LCA with those of ab initio calculations and with measured quantities from SRC-sensitive inclusive electron-scattering data. Conclusions: It is shown that the LCA provides predictions for the SRC scaling factors across the nuclear table that are in line with measured values. In asymmetric nuclei there are sizable differences between the SRC scaling factors for protons and neutrons. It is suggested that this phenomenon may impact the variations of the magnitude of the European Muon Collaboration (EMC) effect across nuclei. Our results corroborate the finding that SRC physics can be qualitatively understood by universal principles that build on local modifications of mean-field wave functions of nucleon pairs. [ABSTRACT FROM AUTHOR]

We investigate the factorization properties of the exclusive electroinduced two-nucleon knockout reaction A(e,e' pN). A factorized expression for the cross section is derived and the conditions for factorization are studied. The A(e,e' pN) cross section is shown to be proportional to the conditional center-of-mass (c.m.) momentum distribution for close-proximity pairs in a state with zero relative orbital momentum and zero radial quantum number. The width of this conditional c.m. momentum distribution is larger than the one corresponding with the full c.m. momentum distribution. It is shown that the final-state interactions (FSIs) only moderately affect the shape of the factorization function for the A(e,e' pN) cross sections. Another prediction of the proposed factorization is that the mass dependence of the A(e,e' pp) [A(e,e' pn)] cross sections is much softer than z(z-1)/2 [NZ]. [ABSTRACT FROM AUTHOR]

We present a method that offers perspectives to perform fully antisymmetrized simulations tor inhomogeneous bulk fermion matter. The technique bears resemblance to classical periodic boundary conditions, using localized single-particle states. Such localized states are an ideal tool to discuss phenomena where spatial localization plays an important role. The antisymmetrization is obtained introducing a doubly periodic structure in the many-body fermion wave functions. This results in circulant matrices for the evaluation of expectation values, leading to a computationally tractable formalism to study fully antisymmetrized bulk fermion matter. We show that the proposed technique is able to reproduce essential fermion features in an elegant and computationally advantageous manner. [ABSTRACT FROM AUTHOR]

We suggest that the number of correlated nucleon pairs in an arbitrary nucleus can be estimated by counting the number of proton-neutron, proton-proton, and neutron-neutron pairs residing in a relative S state. We present numerical calculations of those amounts for the nuclei 4He, 9Be, 12C, 27Al, 40Ca, 48Ca, 56Fe, 63Cu, 108Ag, and 197Au. The results are used to predict the values of the ratios of the per-nucleon electron-nucleus inelastic scattering cross section to the deuteron in the kinematic regime where correlations dominate. [ABSTRACT FROM AUTHOR]

Background: Exclusive two-nucleon knockout after electroexcitation of nuclei [A(e,e'NN) in brief] is considered to be a primary source of information about short-range correlations (SRCs) in nuclei. For a proper interpretation of the data, final-state interactions (FSIs) need to be theoretically controlled. Purpose: Our goal is to quantify the role of FSI effects in exclusive A(e,e'pN) reactions for four target nuclei representative of the whole mass region. Our focus is on processes that are SRC driven. We investigate the role of FSIs for two characteristic detector setups corresponding to "small" and "large" coverage of the available phase space. Method: Use is made of a factorized expression for the A(e,e'pN) cross section that is proportional to the two-body center-of-mass (c.m.) momentum distribution of close-proximity pairs. The A(e,e'pp) and A(e,e'pn) reactions for the target nuclei 12C,27Al,56Fe, and 208Pb are investigated. The elastic attenuation mechanisms in the FSIs are included using the relativistic multiple-scattering Glauber approximation (RMSGA). Single-charge exchange (SCX) reactions are also included. We introduce the nuclear transparency TApN, defined as the ratio of exclusive (e,e'pN) cross sections on nuclei to those on "free" nucleon pairs, as a measure for the aggregated effect of FSIs in pN knockout reactions from nucleus A. A toy model is introduced in order to gain a better understanding of the A dependence of TApN. Results: The transparency TApN drops from 0.2-0.3 for 12C to 0.04-0.07 for 208Pb. For all considered kinematics, the mass dependence of TApN can be captured by the power law TApN∝A-λ with 0.4≲λ≲0.5. Apart from an overall reduction factor, we find that FSIs only modestly affect the distinct features of SRC-driven A(e,e'pN) which are dictated by the c.m. distribution of close-proximity pairs. Conclusion: The SCX mechanisms represent a relatively small (order of a few percent) contribution of SRC-driven A(e,e'pN) processes. The mass dependence of FSI effects in exclusive A(e,e'pN) can be captured in a robust power law and is in agreement with the predictions obtained in a toy model. [ABSTRACT FROM AUTHOR]

A Bayesian analysis of the world's p(y, K+)A data is presented. From the proposed selection of 11 resonances, we find that the following nucleón resonances have the highest probability of contributing to the reaction: S11(1535), S11(1650), F15(1680), P13(1720), D13(1900), P13(1900), P11(1900), and F15 (2000). We adopt a Regge-plus-resonance framework featuring consistent couplings for nucleón resonances up to spin J = 5/2. We evaluate all possible combinations of 11 candidate resonances. The best model is selected from the 2048 model variants by calculating the Bayesian evidence values against the world's p{γ, K+)Λ data. [ABSTRACT FROM AUTHOR]

Abstract: We present a novel method to study the dynamics of bulk fermion systems such as the neutron star’s crust. By introducing periodic boundary conditions into Fermionic Molecular Dynamics, it becomes possible to examine the long-range many-body correlations induced by antisymmetrisation in bulk fermion systems. The presented technique treats the spins and the fermionic nature of the nucleons explicitly and permits investigating the dynamics of the system. Despite the increased complexity related to the periodic boundary conditions, the proposed formalism remains computationally feasible. [Copyright &y& Elsevier]