Electron-nucleon Cross Section Research Articles

Single-pion production in electron-proton interactions

This paper presents an extension of the MK single-pion production model [Kabirnezhad, Phys. Rev. D 97, 013002 (2018); Phys. Rev. D 102, 053009 (2020)] to high hadron invariant mass ($W$) and high momentum transfer (${Q}^{2}$) to conform to the predictions of perturbative QCD due to the quark-hadron duality evidence. New form factors for several resonances and nonresonant background in the electron-nucleon cross sections are determined taking into account the experimental data and improved evaluation techniques. Fits to electron-proton scattering data are used to constrain free parameters and to assign the related uncertainties of the model. The results from this work can be used to determine the vector current in the corresponding neutrino-nucleon cross sections, which is an important input for event generators in long-baseline neutrino-oscillation measurements.

“Hammer” events, neutrino energies, and nucleon-nucleon correlations

Neutrino oscillation measurements depend on a difference between the rate of neutrino-nucleus interactions at different neutrino energies or different distances from the source. Knowledge of the neutrino energy spectrum and neutrino-detector interactions are crucial for these experiments. Short range nucleon-nucleon correlations in nuclei (SRC) affect properties of nuclei. The ArgoNeut liquid Argon Time Projection Chamber (lArTPC) observed neutrino-argon scattering events with two protons back-to-back in the final state ("hammer" events) which they associated with SRC pairs. The MicroBoone lArTPC will measure far more of these events. We simulate hammer events using two simple models. We use the well-known electron-nucleon cross section to calculate e-argon interactions where the e- scatters from a proton, ejecting a pi+, and the pi+ is then absorbed on a moving deuteron-like $np$ pair. We also use a model where the electron excites a nucleon to a Delta, which then deexcites by interacting with a second nucleon. The pion production model results in two protons very similar to those of the hammer events. These distributions are insensitive to the momentum of the $np$ pair that absorbed the $\pi$. The incident neutrino energy can be reconstructed from just the outgoing lepton. The Delta process results in two protons that are less similar to the observed events. ArgoNeut hammer events can be described by a simple pion production and reabsorption model. These hammer events in MicroBooNE can be used to determine the incident neutrino energy but not to learn about SRC. We suggest that this reaction channel could be used for neutrino oscillation experiments to complement other channels with higher statistics but different systematic uncertainties.

Quasielastic electron-deuteron scattering in the weak-binding approximation

We perform a global analysis of all available electron-deuteron quasielastic scattering data using Q^2-dependent smearing functions that describe inclusive inelastic e-d scattering within the weak binding approximation. We study the dependence of the cross sections on the deuteron wave function and the off-shell extrapolation of the elastic electron-nucleon cross sections, which show particular sensitivity at x >> 1. The excellent overall agreement with data over a large range of Q^2 and x suggests a limited need for effects beyond the impulse approximation, with the possible exception of the very high-x or very low-Q^2 regions, where short-distance effects or scattering from non-nucleonic constituents in the deuteron become more relevant.

Improved low Q2 model for neutrino and electron nucleon cross sections in few GeV region

We present an improved model on neutrino- and electron-nucleon scattering cross sections using effective leading order PDFs with a new scaling variable xi_w. Non-perturbative QCD effects at low Q^2 are separately treated for u and d valence quarks, and sea quarks. The improved model uses all inelastic charged lepton F_2 data (SLAC/BCDMS/NMC/HERA), and photoproduction data on proton and deuterium. In this way, we obtain an improved model which describes all inelastic scattering charged lepton data, JLAB resonance data, and neutrino data. This improved model is expected to be better for neutrino oscillation experiments at few GeV region.

Transverse asymmetry of $^3\!\stackrel{\rightarrow}{\rm He}$ and the magnetic form factor of the neutron

Preliminary calculations of the inclusive electromagnetic responses by a polarized 3He target, including final state interaction effects, relativistic kinematics and a relativistic electron-nucleon cross section, are presented. The features of our approach will be briefly illustrated, in order to yield an insight on the model dependence affecting the extraction of the neutron magnetic form factor, G n M , from the inclusive scattering of polarized electrons by a polarized 3He target, recently explored at TJLAB for \(0.1 ~(GeV/c)^2 \le Q^2 \le 0.6 ~(GeV/c)^2\).

Double-scattering contribution tob1(x,Q2)in the deuteron

We study the tensor structure function ${b}_{1}{(x,Q}^{2})$ in deep inelastic scattering of an electron from a polarized deuteron target. We model the electron-nucleon cross section at the starting point for ${Q}^{2}$ evolution by vector-meson dominance. Shadowing due to the double scattering of vector mesons, along with the presence of a $d$-state admixture in a ground-state deuteron wave function gives rise to a nonvanishing contribution to ${b}_{1}{(x,Q}^{2})$. We find a large enhancement at low $x$ in qualitative agreement with other recent estimates of double-scattering contributions to ${b}_{1}{(x,Q}^{2})$. If the model is valid, it should apply within the range of present fixed-target experiments.

Electron-nucleon cross section in (e,e'p) reactions.

We examine commonly used approaches to deal with the scattering of electrons from a bound nucleon. Several prescriptions are shown to be related by gauge transformations. Nevertheless, due to current non-conservation, they yield different results. These differences reflect the size of the uncertainty that persists in the interpretation of $(e,e'p)$ experiments.

Off-shell effects in quasielastic electron nucleus scattering

Using the Ward-Takahashi identity, on-shell condition, bound Dirac equation and off-shell expansion, a reduced version of half off-shell virtual photon nucleon vertex has been suggested. The vertex are decomposed into several different order terms: the on-shell terms, first and second off-shell terms. The off-shell behaviour of the form factors is discussed in the one meson loop model. Using the reduced vertex and parametrized off-shell form factors the quasielastic response functions are calculated for several nuclei at ¦q¦–kf and for56Fe at large ¦q¦ up to 1.14 GeV/c and at −q2=0.9 (GeV/c)2. The Coulomb sums are evaluated and a comparison of the theoretical prediction with data is given. The off-shell electron nucleon cross section is calculated and compared with the “cc1” off-shell extrapolation.

Determination of the scale parameter ΛQCD from elastic electron-proton scattering at high Q2

The form factor predictions of perturbative QCD at asymptotic Q 2 and meson dynamics at low Q 2 are combined to fit the existing data on elastic electron-nucleon cross sections. Taking into account contributions due to the anomalous dimensions of the three-quark component in the nucleon, fits to the data give values of the QCD scale parameter Λ QCD in the range 100–250 MeV.

Off-shell electron-nucleon cross sections: The impulse approximation

With the goal of improving the analysis of quasi-elastic (e, e′) and (e, e′N) experiments, ambiguities in the impulse approximation are investigated by comparing various off-shell extrapolations of the Rosenbluth cross section. It is found that these ambiguities are especially large for low incident electron energies and momentum transfers and that they can be reduced by applying various physical constraints, such as those due to Lorentz invariance and current conservation. In particular the latter is important: most off-shell cross sections that have been used do not treat this correctly and, as a consequence, in the limit of the photon point give infinite photoabsorption cross sections.

Electron-nucleon interaction in quasi-free scattering: (I). Non-relativistic Hamiltonian through second order

In the frame of a program aiming at examining the approximations involved in the theoretical treatment of (e, e′p) reactions, the electron-nucleon interaction producing the knock-out mechanism is considered in the non-relativistic approach of McVoy and Van Hove and compared with the relativistic one based on the one-photon-exchange Feynman graph. In this paper the non-relativistic Hamiltonian through second order in the nucleon recoil velocity is adopted; in the next paper higher order terms are included. The two approaches appear equivalent as far as the usual DWIA cross section is concerned, where a factorization occurs between the electron-nucleon cross section and the nucleon momentum distribution. However the unfactorized DWIA cross section behaves differently. This is attributed to a different off-shell behaviour of the two scattering amplitudes.

Comparison of high-energy electron and muon inelastic nuclear scatterings

The inelastic scattering of 2.3, 5.0, and 13.6 GeV electrons are compared with that of 3.0, 8.0, and 10.1 GeV muons in nuclear emulsions. The partial and integral cross sections have been measured for all the beams and are compared with theory by using the first, second, and fourth power of $\frac{1}{(\frac{1+{q}^{2}}{m_{\ensuremath{\rho}}^{}{}_{}{}^{2}})}$ for ${\ensuremath{\sigma}}_{\mathrm{exp}}({q}^{2},\ensuremath{\nu})$, the quantity commonly called the "virtual-photon-nucleon total cross section." The muon-nucleon cross sections on the average are slightly smaller than the electron-nucleon cross sections. Experimentally no significant difference between the behavior of the muon and the electron in the inelasttic scattering has been found.

Improved Sum Rule for Electron-Deuteron Scattering

A qualitative discussion of the approximations implicit in the present theoretical treatment of the deuteron is presented. An improved sum rule which relates the total elastic and inelastic scattering of electrons from the deuteron to the free electron-nucleon cross sections is derived. It has the property of reducing to the correct relativistic result upon neglect of binding. It is proved that the use of folded nucleon and nuclear form factors is correct. It is shown that the finite nucleon size does not affect any real photon process.

High energy electron scattering by polarized nuclei

Experiments on the elastic scattering of high energy electrons by nuclei have been recently carried out (1), giving relevant information about the nuclear charge distribution (z). Unti l now only unpolarized target nuclei have been used, so only the radial charge distribution could be studied. I t has been possible, recently, to align nuclei of paramagnetic substances to a high degree (a). Therefore the measurement of the azimuthal dependence of electron-nucleon cross-section due t , the asymmetry in the nuclear charge distribution has come within the range . f the actual experimental possibilities. The calculation of the electron scattering cross-section by a given asym~netri(. charge distribution involves the solution of the following Dirae equation: