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Register a new userUnified description of electron-nucleus scattering within the spectral function formalism
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We developed a novel approach based on a generalization of factorization and nuclear spectral functions, allowing for a consistent treatment of the amplitudes involving one- and two-nucleon currents, whose contribution to the nuclear electromagnetic response in the transverse channel is known to be significant. We report the results of calculations of the inclusive electron-carbon cross section, showing that the inclusion of processes involving two-nucleon currents appreciably improves the agreement between theory and data in the dip region, between the quasi elastic and $Delta$-production peaks. The implications for the analysis of neutrino-nucleus cross sections are discussed.
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We illustrate the connection between electron and neutrino scattering off nuclei and show how the former process can be used to constrain the description of the latter. After reviewing some of the nuclear models commonly used to study lepton-nucleus reactions, we describe in detail the SuSAv2 model and show how its predictions compare with the available electron- and neutrino-scattering data over the kinematical range going from the quasi-elastic peak to pion-production and highly inelastic scattering.
We compute inclusive electron-nucleus cross sections using ab initio spectral functions of $^4$He and $^{16}$O obtained within the Self Consistent Greens Function approach. The formalism adopted is based on the factorization of the spectral function and the nuclear transition matrix elements. This allows to provide an accurate description of nuclear dynamics and to account for relativistic effects in the interaction vertex. Our calculations use a saturating chiral Hamiltonian in order reproduce the correct nuclear sizes. When final state interactions for the struck particle are accounted for, we find nice agreement between the data and the theory for the inclusive electron-$^{16}$O cross section. The results lay the foundations for future applications of the Self Consistent Greens Function method, in both closed and open shell nuclei, to neutrino data analysis. This work also presents results for the point-proton, charge and single-nucleon momentum distribution of the same two nuclei. The center of mass can affect these quantities for light nuclei and cannot be separated cleanly in most ab initio post-Hartree-Fock methods. In order to address this, we developed a Metropolis Monte Carlo calculation in which the center of mass coordinate can be subtracted exactly from the trial wave function and the expectation values. We gauged this effect for $^4$He by removing the center of mass effect from the Optimal Reference State wave function that is generated during the Self Consistent Greens Function calculations. Our findings clearly indicate that the residual center of mass contribution strongly modifies calculated matter distributions with respect to those obtained in the intrinsic frame. Hence, its subtraction is crucial for a correct description of light nuclei.
The distorted spin-dependent spectral function of a nucleon inside an A=3 nucleus is introduced as a novel tool for investigating the polarized electron scattering off polarized $^3$He in semi-inclusive DIS regime (SiDIS), going beyond the standard plane wave impulse approximation. This distribution function is applied to the study of the spectator SiDIS, $vec{^3{rm He}}(vec e, e ~{^2}{rm H})X$, in order to properly take into account the final state interaction between the hadronizing quark and the detected deuteron, with the final goal of a more reliable extraction of the polarized parton-distribution $g_1(x)$ inside a bound proton. Our analysis allows to single out two well-defined kinematical regions where the experimental asymmetries could yield very interesting information: the region where the final state effects can be minimized, and therefore the direct access to the parton distributions in the proton is feasible, and the one where the final state interaction dominates, and the spectator SiDIS reactions can elucidate the mechanism of the quark hadronization itself. The perspectives of extending our approach i) to the mirror nucleus, $^3$H, for achieving a less model-dependent flavor decomposition, and ii) to the asymmetries measured in the standard SiDIS reactions, $vec e + vec{^3 {rm He}} to e + h+X$ with $h$ a detected fast hadron, with the aim of extracting the neutron transversity, are discussed.
Scaling features of the nuclear electromagnetic response functions unveil aspects of nuclear dynamics that are crucial for interpretating neutrino- and electron-scattering data. In the large momentum-transfer regime, the nucleon-density response function defines a universal scaling function, which is independent of the nature of the probe. In this work, we analyze the nucleon-density response function of $^{12}$C, neglecting collective excitations. We employ particle and hole spectral functions obtained within two distinct many-body methods, both widely used to describe electroweak reactions in nuclei. We show that the two approaches provide compatible nucleon-density scaling functions that for large momentum transfers satisfy first-kind scaling. Both methods yield scaling functions characterized by an asymmetric shape, although less pronounced than that of experimental scaling functions. This asymmetry, only mildly affected by final state interactions, is mostly due to nucleon-nucleon correlations, encoded in the continuum component of the hole SF.
We present a model for electron- and neutrino-scattering off nucleons and nuclei focussing on the quasielastic and resonance region. The lepton-nucleon reaction is described within a relativistic formalism that includes, besides quasielastic scattering, the excitation of 13 N* and Delta resonances and a non-resonant single-pion background. Recent electron-scattering data is used for the state-of-the-art parametrizations of the vector form factors; the axial couplings are determined via PCAC and, in the case of the Delta resonance, the axial form factor is refitted using neutrino-scattering data. Scattering off nuclei is treated within the GiBUU framework that takes into account various nuclear effects: the local density approximation for the nuclear ground state, mean-field potentials and in-medium spectral functions. Results for inclusive scattering off Oxygen are presented and, in the case of electron-induced reactions, compared to experimental data and other models.
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