M. B. Barbaro

Inelastic ν and ν scattering on nuclei and “strangeness” of the nucleon

Abstract Possibilities to extract information on the strange form factors of the nucleon from neutrino (anti-neutrino) inelastic scattering on nuclei, in an energy range from 200 MeV to 1 GeV and more, are investigated in detail. All calculations are performed within two relativistic independent particle models (Fermi gas and shell model); the final state interactions of the ejected nucleon are taken into account through relativistic optical model potentials. We have shown that the values of the cross sections significantly depend on the nuclear model (especially in the lower energy range). However, the NC/CC neutrino-anti-neutrino asymmetry in a medium-high energy range shows a rather small dependence on the model and allows to disentangle different values of the parameters that characterize the strange form factors. We have calculated also the ratio of the cross sections for inelastic NC scattering of neutrinos on nuclei, with the emission of a proton and of a neutron. Our calculations show that at high neutrino energy this ratio depends rather weakly on the nuclear model and confirm previous conclusions on the rather strong dependence of this ratio upon the axial strange form factors; however, at E ν ⩽ 200 MeV, the FSI are found to significantly affect the ratio.

Relativistic descriptions of final-state interactions in charged-current quasielastic neutrino-nucleus scattering at MiniBooNE kinematics

The results of two relativistic models with different descriptions of the final-state interactions are compared with the MiniBooNE data of charged-current quasielastic cross sections. The relativistic mean field model uses the same potential for the bound and ejected nucleon wave functions. In the relativistic Greens function model, the final-state interactions are described in the inclusive scattering consistently with the exclusive scattering using the same complex optical potential. The relativistic Greens function results describe the experimental data for total cross sections without the need to modify the nucleon axial mass.

The ratio of p and n yields in NC neutrino (anti-neutrino) nucleus scattering and strange form-factors of the nucleon

Abstract We calculate the ratio of proton and neutron yields in NC induced ν ( ν )–nucleus inelastic scattering at neutrino energies of about 1 GeV. We show that this ratio depends very weakly on the nuclear models employed and that in ν and ν cases the ratios have different sensitivity to the axial and vector strange form factors; moreover the ratio of ν –nucleus cross sections turns out to be rather sensitive to the electric strange form factor. We demonstrate that measurements of these ratios will allow to get information on the strange form factors of the nucleon in the region Q 2 ≥0.4 GeV 2 .

Strange form factors of the proton: a new analysis of the ν (ovrarr/BC) data of the BNL-734 experiment

Abstract We consider ratios of elastiv ν ( ovrarr / BC )-proton cross sections measured by the Brookhaven BNL-734 experiment and use them to obtain the neutral current (NC) over charged current (CC) neutrino-antineutrino asymmetry. We discuss the sensitivity of these ratios and of the asymmetry to the electric, magnetic and axial strange form factors of the nucleon and to the axial cutoff mass M A . We show that the effects of the nuclear structure and interactions on the asymmetry and, in general, on ratios of cross sections are negligible. We find some restrictions on the possible values of the parameters characterizing the strange form factors. We show that a precise measurement of the neutrino-antineutrino asymmetry would allow the extraction of the axial and vector magnetic strange form factors in a model independent way. The neutrino-antineutrino asymmetry turns out to be almost independent on the electric strange form factor and on the axial cutoff mass.

Influence of nucleonic motion in relativistic Fermi gas inclusive responses

Abstract Impulsive hadronic descriptions of electroweak processes in nuclei involve two distinctly different elements: one stems from the nuclear many-body physics — the medium — which is rather similar for the various inclusive response functions, and the other embodies the responses of the hadrons themselves to the electroweak probe and varies with the channel selected. In this Letter we investigate within the context of the relativistic Fermi gas in both the quasi-elastic and N→Δ regimes the interplay between these two elements. Specifically, we focus on expansions in the one small parameter in the problem, namely, the momentum of a nucleon in the initial wave function compared with the hadronic scale, the nucleon mass. Both parity-conserving and -violating inclusive responses are studied and the interplay between longitudinal (L) and transverse (T and T′) contributions is highlighted.

Superscaling in electron-nucleus scattering and its link to CC and NC QE neutrino-nucleus scattering

The superscaling approach (SuSA) to neutrino-nucleus scattering, based on the assumed universality of the scaling function for electromagnetic and weak interactions, is reviewed. The predictions of the SuSA model for bot CC and NC differential and total cross sections are presented and compared with the MiniBooNE data. The role of scaling violations, in particular the contribution of meson exchange currents in the two-particle two-hole sector, is explored.

Asymmetric relativistic Fermi gas model for quasielastic lepton-nucleus scattering

We develop an asymmetric relativistic Fermi gas model for the study of the electroweak nuclear response in the quasielastic region. The model takes into account the differences between neutron and proton densities in asymmetric (N > Z) nuclei, as well as differences in the neutron and proton separation energies. We present numerical results for both neutral and charged current processes, focusing on nuclei of interest for ongoing and future neutrino oscillation experiments. We point out some important differences with respect to the commonly employed symmetric Fermi gas model.

Relativistic Modeling of Inclusive Neutrino-Nucleus Interactions in the SuperScaling Approach

We present our recent progresses on the relativistic modeling of neutrino-nucleus reactions (G.D. Megias et al., Phys. Lett. B, 725:170–174, 2003; Phys. Rev. D 89:093002, 2014; M.V. Ivanov et al., Phys. Rev. C 89:014607, 2014; R. Gonzalez-Jimenez et al., Phys. Rev. C 90:035501, 2014; G.D. Megias et al., Phys. Rev. D 91;073004, 2015; M.V. Ivanov et al., J. Phys. G 43:045101, 2016; A.M. Ankowski et al., Phys. Rev. C 92;025501, 2015) and comparisons with high precision experimental data in a wide energy range (0–100 GeV).

Lepton mass effects in the Bethe-Heitler process

Abstract We develop the full finite lepton mass formalism for the production of real photons via the Bethe–Heitler reaction of unpolarized leptons off unpolarized nucleons. Genuine lepton mass effects are described, in particular their dependence upon the lepton mass and the initial beam energy, as well as their sensitivity to the nucleon isospin. In the minimum momentum transfer region, these effects dominate the muon induced proton cross section and become significant for electron scattering at small x B .

Scaling ideas in neutrino scattering reactions: application to the MiniBooNE experiment

An exhaustive analysis of the world data on electron scattering has shown that scaling and superscaling properties are fulfilled with great accuracy. The relativistic impulse approximation (RIA) yields a satisfactory description of experimental data. Not only scaling and superscaling behavior emerge, but also the specific asymmetric shape of the experimental scaling function is reproduced. In this work two relativistic approaches are considered to evaluate the neutrino-nucleus cross sections. One, based on the relativistic impulse approximation, relies on the microscopic description of nuclear dynamics using relativistic mean field theory, and incorporates a description of final state interactions. The second is based on the superscaling behavior exhibited by electron scttering data and its applicability, due to the universal character of the scaling function, to the analysis of neutrino scattering reactions. The role played by the vector meson-exchange currents in the two-particle two-hole sector is also incorporated and the results obtained are compared with the recent data for neutrinos measured by the MiniBooNE Collaboration.