[en] Polarized electron-deuteron deep-inelastic scattering (DIS) with detection of the spectator proton ("tagged DIS") enables measurements of neutron spin structure with maximal control of nuclear effects. We calculate the longitudinal spin asymmetries in polarized tagged DIS using methods of light-front nuclear structure and study their dependence on the measured proton momentum. Asymmetries can be formed with all three deuteron spin states (± 1, 0) or the two maximum-spin states only (± 1, involving tensor polarization). The proton momentum dependence can be used to select pure S-wave configurations in the deuteron and eliminate D-wave depolarization (transverse momenta p_pT ≲ 100 MeV). Free neutron spin structure can be extracted model-independently through pole extrapolation of the tagged asymmetries. Such measurements could be performed at a future electron-ion collider (EIC) with polarized deuteron beams and forward proton detectors.

[en] An approximate method to quantify the mass dependence of the number of two-nucleon (2N) short-range correlations (SRC) in nuclei is suggested. The proposed method relies on the concept of the “local nuclear character” of the SRC. We quantify the SRC and its mass dependence by computing the number of independent-particle model (IPM) nucleon pairs in a zero relative orbital momentum state. We find that the relative probability per nucleon for 2N SRC follows a power law as a function of the mass number A. The predictions are connected to measurements which provide access to the mass dependence of SRC. First, the ratio of the inclusive inelastic electron scattering cross sections of nuclei to "2H at large values of the Bjorken variable. Second, the EMC effect, for which we find a linear relationship between its magnitude and the predicted number of SRC-prone pairs. (author)

[en] Semi-inclusive deep inelastic scattering off the deuteron with production of a slow nucleon in recoil kinematics is studied in the virtual nucleon approximation, in which the final-state interaction (FSI) is calculated within generalized eikonal approximation. The cross section is derived in a factorized approach, with a factor describing the virtual photon interaction with the off-shell nucleon and a distorted spectral function accounting for the final-state interactions. One of the main goals of the study is to understand how much the general features of the diffractive high-energy soft rescattering accounts for the observed features of FSI in deep inelastic scattering (DIS). Comparison with the Jefferson Lab data shows good agreement in the covered range of kinematics. Most importantly, our calculation correctly reproduces the rise of the FSI in the forward direction of the slow nucleon production angle. By fitting our calculation to the data we extracted the W and Q² dependencies of the total cross section and slope factor of the interaction of DIS products, X, off the spectator nucleon. This analysis shows the XN-scattering cross section rising with W and decreasing with an increase of Q². Finally, our analysis points at a largely suppressed off-shell part of the rescattering amplitude.

[en] We present a selection of results obtained within the context of a relativistic eikonal model. First, results of relativistic Glauber calculations for the nuclear transparency extracted from photon-induced pion production are presented. Second, computed differential cross-sections for the ¹²C(p,2p) are compared to data. (orig.)

[en] We sketch an approximate method to quantify the number of correlated pairs in any nucleus A. It is based on counting independent-particle model (IPM) nucleon-nucleon pairs in a relative S-state with no radial excitation. We show that IPM pairs with those quantum numbers are most prone to short-range correlations and are at the origin of the high-momentum tail of the nuclear momentum distributions. Our method allows the calculation of the a_2 ratios extracted from inclusive electron scattering. Furthermore, our results reproduce the observed linear correlation between the number of correlated pairs and the magnitude of the EMC (European Muon Collaboration) effect. We show that the width of the pair center-of-mass distribution in exclusive two-nucleon knockout yields information on the quantum numbers of the pairs. (authors)

[en] A relativistic and quantum mechanical framework to compute nuclear transparencies for pion photo- and electroproduction reactions is presented. Final-state interactions for the ejected pions and nucleons are implemented in a relativistic eikonal approach. At sufficiently large ejectile energies, a relativistic Glauber model can be adopted. At lower energies, the framework possesses the flexibility to use relativistic optical potentials. The proposed model can account for the color-transparency (CT) phenomenon and short-range correlations (SRC) in the nucleus. Results are presented for kinematics corresponding to completed and planned experiments at Jefferson Lab. The influence of CT and SRC on the nuclear transparency is studied. Both the SRC and CT mechanisms increase the nuclear transparency. The two mechanisms can be clearly separated, though, as they exhibit a completely different dependence on the hard-scale parameter. The nucleon and pion transparencies as computed in the relativistic Glauber approach are compared with optical-potential and semiclassical calculations. The similarities in the trends and magnitudes of the computed nuclear transparencies indicate that they are not subject to strong model dependences

[en] The authors present a relativistic and cross-section factorized framework for computing quasielastic A(p,pN) observables at intermediate and high energies. The model is based on the eikonal approximation and can accommodate both optical potentials and the Glauber method for dealing with the initial- and final-state interactions (IFSI). At lower nucleon energies, the optical-potential philosophy is preferred; whereas at higher energies, the Glauber method is more natural. This versatility in dealing with the IFSI allows one to describe A(p,pN) reactions in a wide energy range. Most results presented here use optical potentials, as this approach is argued to be the optimum choice for the kinematics of the experiments considered in the present paper. The properties of the IFSI factor, a function containing the entire effect of the IFSI, are studied in detail. The predictions of the presented framework are compared with two kinematically different experiments. First, differential cross sections for quasielastic proton scattering at 1 GeV off ¹²C, ¹⁶O, and ⁴⁰Ca target nuclei are computed and compared to data from Petersburg Nuclear Physics Institute (PNPI). Second, the formalism is applied to the analysis of a ⁴He(p,2p) experiment at 250 MeV. The optical-potential calculations are found to be in good agreement with the data from both experiments, showing the reliability of the adopted model in a wide energy range

[en] We present a relativistic and cross-section factorized framework for computing nuclear transparencies extracted from A(γ,πN) reactions at intermediate energies. The proposed quantum mechanical model adopts a relativistic extension to the multiple-scattering Glauber approximation to account for the final state interactions of the ejected nucleon and pion. The theoretical predictions are compared against the experimental ⁴He(γ,pπ^-) data from the Thomas Jefferson National Accelerator Facility. For those data, our results show no conclusive evidence of the onset of mechanisms related to color transparency

[en] We give an overview of a model to describe deep-inelastic scattering (DIS) off the deuteron with a spectator proton (e+d → e'+X+p_s), based on the virtual nucleon approximation (VNA). The model accounts for the final-state interactions (FSI) of the DIS debris with the spectator proton. Values of the rescattering cross section are obtained by fits to high-momentum spectator data. By using the so-called 'pole extrapolation' method, free neutron structure functions can be obtained by extrapolating low-momentum spectator proton data to the on-shell neutron pole. We apply this method to the BONuS data set and find a surprising Bjorken x dependence, indicating a possible rise of the neutron to proton structure function ratio at high x. (authors)

[en] We address the issue of nuclear attenuation in nucleon and pion knockout reactions. A selection of results from a model based on a relativistic multiple-scattering approximation is presented. We show transparency calculations for pion electroproduction on several nuclei, where data are in very good agreement with calculations including color transparency. Secondly, we discuss the density dependence of reactions involving one or double proton knockout. The latter reaction succeeds in probing the high density regions in the deep interior of the nucleus. We have shown a selection of results obtained in a model based on relativistic multiple-scattering Glauber scattering theory. The model has no free parameters and can be applied to variety of reactions, with leptonic and hadronic beams and outgoing nucleons and/or pions. Our calculations show that relativity plays a rather modest role in the magnitude of nuclear attenuation. We showed very good agreement of pion transparencies with calculations including colour transparency. Secondly, we exploited the robustness of the model to explore which target-nucleus densities can be effectively probed in knockout reactions involving one, two and three protons. We find that the A(γ, pp) reaction probes the interior of the target nucleus, the A(p, 2p) is rather peripheral, whereas the A(e, e' p) is somewhat intermediate between these two. (author)