Inclusive Electron Research Articles

Quasielastic electron scattering at high energy from12C,56Fe,and197Au

A relativistic mean-field single particle knockout model is compared to inclusive electron scattering ${(e,e}^{\ensuremath{'}})$ from a range of nuclei ${(}^{12}\mathrm{C},$ ${}^{56}\mathrm{Fe},$ and ${}^{197}\mathrm{Au})$ at high electron energy, but in kinematics where the cross section is dominated by the quasielastic response. These experiments were done with incident electron energies of approximately 2 GeV at SLAC with four-momentum transfer squared of approximately $0.20--0.30(\mathrm{GeV}{/c)}^{2}.$ We include the effects of electron Coulomb distortion in the calculation, and propose a simple way of including Coulomb distortion at high energies which can be used to analyze newer ${(e,e}^{\ensuremath{'}})$ experiments at Jefferson Lab. The effects of the predicted weakening of the strong scalar and vector potentials of the $\ensuremath{\sigma}\ensuremath{-}\ensuremath{\omega}$ model at high nucleon kinetic energy are included in our model.

Inclusive electron scattering in a relativistic Green’s function approach

A relativistic Green function approach to the inclusive quasielastic (e,e') scattering is presented. The single particle Green function is expanded in terms of the eigenfunctions of the nonhermitian optical potential. This allows one to treat final state interactions consistently in the inclusive and in the exclusive reactions. Numerical results for the response functions and the cross sections for different target nuclei and in a wide range of kinematics are presented and discussed in comparison with experimental data.

Do Ordinary Nuclei Contain Exotic States of Matter?

The strongly repulsive core of the short-range nucleon-nucleon interaction leads to the existence of high-momentum nucleons in nuclei. Inclusive electron scattering can be used to probe these high-momentum nucleons and study the nature of the corresponding short-range correlations in nuclei. With recent data from Jefferson Lab we have begun to map out the strength of two-nucleon correlations in nuclei, while upcoming experiments should allow us to isolate the presence of multi-nucleon correlations. In addition to their importance in describing nuclear structure, these configurations of correlated nucleons represent high density 'droplets' of hadronic matter. As the density of hadronic matter increases there should be a weakening of quark confinement, similar to the onset of deconfinement expected at extremely high temperatures. While there have been hints of non-hadronic structure in nuclei, future measurements will allow us to directly probe the quark distributions of high density configurations in nuclei. A modified quark structure in these closely packed nucleons would provide a clear signature of exotic components to the structure of nuclei.

Delta-isobar relativistic meson exchange currents in quasielastic electron scattering

We study the role of the Δ-isobar current on the response functions for high energy inclusive quasielastic electron scattering from nuclei. We consider a general Lagrangian which is compatible with contact invariance and perform a fully relativistic calculation in first-order perturbation theory for one-particle emission. The dependence of the responses upon off-shell parametrizations is analyzed and found to be mild. A discussion of scaling behaviour and a comparison with various non-relativistic approaches are also presented.

Measurement of the branching fraction for inclusive semileptonicBmeson decays

A largely model-independent measurement of the inclusive electron momentum spectrum and branching fraction for semileptonic decays of B mesons is presented based on data recorded at the Υ(4S) resonance with the BABAR detector. Backgrounds from secondary charm decays are separated from prompt B decays using charge and angular correlations between the electron from one B meson and a high momentum electron tag from the second B meson. The resulting branching fraction is B(B→Xeν)=[10.87±0.18(stat)±0.30(syst)]%. Based on this measurement we determine the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |Vcb|. Received 14 August 2002DOI:https://doi.org/10.1103/PhysRevD.67.031101©2003 American Physical Society

Resonance region to DIS, quark-hadron duality at Jefferson Lab

New measurements of inclusive electron scattering on the proton and deuteron have been made at Jefferson Lab with a four-momentum transfer range of 0.3 ≤ Q 2 ≤ 4.5 (GeV/ c) 2 as a study of quark-hadron duality at low Q 2. The F 2 structure function is found to scale about a common scaling curve down to Q 2 of 0.5 (GeV/ c) 2, indicating that higher twist effects are small. Duality in other observables and in electron scattering on nuclei are also discussed.

Excitation of the Δ resonance in inclusive ed scattering

The parameters of the pion-electroproduction peak in the cross section for inclusive electron scattering on 1H and d target nuclei are determined for various kinematical conditions of measurements. It is shown that, for low 4-momentum transfers, 0.030≤Q2≤0.086 (GeV/c)2, the Q2 dependence of the shift of the pion-electroproduction peak in the πN invariant mass for a deuteron target with respect to that for a free proton does not exhibit a universal behavior that is characteristic of complex nuclei.

Longitudinal and transverse quasielastic response functions of light nuclei

The ${}^{3}\mathrm{He}$ and ${}^{4}\mathrm{He}$ longitudinal and transverse response functions are determined from an analysis of the world data on quasielastic inclusive electron scattering. The corresponding Euclidean response functions are derived and compared to those calculated with Green's function Monte Carlo methods, using realistic interactions and currents. Large contributions associated with two-body currents are found, particularly in the ${}^{4}\mathrm{He}$ transverse response, in agreement with data. The contributions of the two-body charge and current operators in the ${}^{3}\mathrm{He},$ ${}^{4}\mathrm{He},$ and ${}^{6}\mathrm{Li}$ response functions are also studied via sum-rule techniques. A semiquantitative explanation for the observed systematics in the excess of transverse quasielastic strength, as function of mass number and momentum transfer, is provided. Finally, a number of model studies with simplified interactions, currents, and wave functions are carried out to elucidate the role played, in the full calculation, by tensor interactions and correlations.

Extended superscaling of electron scattering from nuclei

An extended study of scaling of the first and second kinds for inclusive electron scattering from nuclei is presented. Emphasis is placed on the transverse response in the kinematic region lying above the quasielastic peak. In particular, for the region in which electroproduction of resonances is expected to be important, approximate scaling of the second kind is observed and the modest breaking of it is shown probably to be due to the role played by an inelastic version of the usual scaling variable.

INCLUSIVE ELECTRON NEUTRINO REACTIONS IN NUCLEI AND THE NEUTRON NUMBER

We compare the inclusive electron neutrino cross sections, νe+Ni→X + e-, averaged over the Michel spectrum for 12 C , 13 C , 56 Fe and 127 I . We choose these nuclei because terrestrial measurements at LSND and KARMEN have been undertaken for them and these measurements are in reasonable agreement with calculated values. We show that the cross sections increase linearly with neutron number for these nuclei and discuss what this might imply.

Xandξscaling of the nuclear structure function at largex

Inclusive electron scattering data are presented for ^2H and Fe targets at an incident electron energy of 4.045 GeV for a range of momentum transfers from Q^2 = 1 to 7 (GeV/c)^2. Data were taken at Jefferson Laboratory for low values of energy loss, corresponding to values of Bjorken x greater than or near 1. The structure functions do not show scaling in x in this range, where inelastic scattering is not expected to dominate the cross section. The data do show scaling, however, in the Nachtmann variable \xi. This scaling may be the result of Bloom Gilman duality in the nucleon structure function combined with the Fermi motion of the nucleons in the nucleus. The resulting extension of scaling to larger values of \xi opens up the possibility of accessing nuclear structure functions in the high-x region at lower values of Q^2 than previously believed.

Neutrino oscillation results from LSND

The Liquid Scintillator Neutrino Detector took data during the years 1993 through 1998. The results of a final analysis of the data are reported here. In summary, the analysis resulted in a cleaner sample of decay-at-rest oscillation candidates and provided a strong constraint on beam related backgrounds. The oscillation probability is fitted to the correlated photon parameter in the inclusive electron sample. The fit yields an excess of 83.3±21.2 events attributable to neutrino oscillations. This corresponds to an oscillation probability of (0.25±0.06±0.04)% for that detector and beam configuration.

Inclusive quasielastic electron scattering on 6He: a probe of the halo structure

We investigate inclusive electron scattering reactions on two-neutron halo nuclei in the quasielastic region. Expressions for the cross section and structure functions are given assuming that the halo nucleus can be described as a three-body system (core+ n+ n). The method is applied to 6He. We compute cross sections and structure functions, and investigate the kinematic conditions for which the observables are determined either by α-knockout or by halo neutron-knockout. The optimal kinematical domain to disantangle the momentum distributions of the various components of the three-body system ( q≲200 MeV/c and ω< q 2/2 M N +20 MeV) are explored.

Ground state correlations and mean field in16O.II. Effects of a three-nucleon interaction

We continue the investigations of the $^{16}$O ground state using the coupled-cluster expansion [$\exp({\bf S})$] method with realistic nuclear interaction. In this stage of the project, we take into account the three nucleon interaction, and examine in some detail the definition of the internal Hamiltonian, thus trying to correct for the center-of-mass motion. We show that this may result in a better separation of the internal and center-of-mass degrees of freedom in the many-body nuclear wave function. The resulting ground state wave function is used to calculate the "theoretical" charge form factor and charge density. Using the "theoretical" charge density, we generate the charge form factor in the DWBA picture, which is then compared with the available experimental data. The longitudinal response function in inclusive electron scattering for $^{16}$O is also computed.

Precise measurement of the transverse asymmetry A T′ for inclusive quasielastic electron scattering off polarized 3He

We report the preliminary measurement of the 3He inclusive transverse asymmetry A T′ from a recent experiment at Jefferson Lab.

Superscaling of inclusive electron scattering from nuclei

We investigate the degree to which the concept of superscaling, initially developed within the framework of the relativistic Fermi gas model, applies to inclusive electron scattering from nuclei. We find that data obtained from the low energy loss side of the quasielastic peak exhibit the superscaling property, i.e., the scaling functions f(\psi') are not only independent of momentum transfer (the usual type of scaling: scaling of the first kind), but coincide for A \geq 4 when plotted versus a dimensionless scaling variable \psi' (scaling of the second kind). We use this behavior to study as yet poorly understood properties of the inclusive response at large electron energy loss.

Theoretical aspects of inclusive scattering of 4.05 GeV electrons from nuclei

We compare recent CEBAF data on inclusive electron scattering on nuclei with predictions, based on a relation between structure functions (SF) of a nucleus, a nucleon and a nucleus of point-nucleons. The latter contains nuclear dynamics, e.g. binary collision contributions in addition to the asymptotic limit. The agreement with the data is good, except in low-intensity regions. Computed ternary collsion contributions appear too small for an explanation. We perform scaling analyses in Gurvitz's scaling variable and found that for $y_G\gtrless 0$, ratios of scaling functions for pairs of nuclei differ by less than 15-20% from 1. Scaling functions for $<y_G>0$ are, for increasing $Q^2$, shown to approach a plateau from above. We observe only weak $Q^2$-dependence in FSI, which in the relevant kinematic region is ascribed to the diffractive nature of the NN amplitudes appearing in FSI. This renders it difficult to separate asymptotic from FSI parts and seriously hampers the extraction of $n(p)$ from scaling analyses in a model-independnent fashion.

Extraction of nucleon momentum distributions from inclusive electron scattering on nuclei

We address the problem of extracting single-nucleon momentum distributions n( p) from inclusive lepton scattering data. A model for these relates nuclear and nucleon structure functions (SF) through an intermediate SF f PN of a nucleus of point-particles. In addition to the asymptotic limit (AL), f PN contains, generally q-dependent, Final State Interactions (FSI) parts. In the inverse problem we employ the structure of the theory, but no numerical results, in order to separate q-dependent FSI from the AL, which depends on n( p). It appears that in the q-range of the analyzed lepton data, the FSI are only weakly q-dependent, making it virtually impossible to obtain parameters in a free fit of the parametrized components of f. Imposing we obtain n( p) for Fe and 4 He.

Inclusive Electron-Nucleus Scattering at Large Momentum Transfer

Inclusive electron scattering is measured with 4.045 GeV incident beam energy from C, Fe, and Au targets. The measured energy transfers and angles correspond to a kinematic range for Bjorken x>1 and momentum transfers from Q2=1–7(GeV/c)2. When analyzed in terms of the y-scaling function the data show for the first time an approach to scaling for values of the initial nucleon momenta significantly greater than the nuclear matter Fermi momentum (i.e., >0.3GeV/c).Received 13 November 1998DOI:https://doi.org/10.1103/PhysRevLett.82.2056©1999 American Physical Society

The semi-classical approach to the exclusive electron scattering

The semi-classical approach, successfully applied in the past to the inelastic, inclusive electron scattering off nuclei, is extended to the treatment of exclusive processes. The associated formalism goes beyond the plane wave impulse approximation, since it can account also for the final states interaction in the mean field approximation, respecting the Pauli principle. We then explore, in the frame of two admittedly crude approximations, the impact on the exclusive cross section of the distortion of the outgoing nucleon wave. In addition also the influence, on the same observable, of the shape of the potential binding the nucleons into the nucleus is investigated. In accord with the findings of fully quantum mechanical calculations, the exclusive scattering is found to be quite sensitive to the mean field final states interaction, unlike the inclusive one. Indeed we verify that the latter is not affected, as implied by unitarity, by the distortion of the outgoing nucleon wave except for the effect of relativity, which is modest in the range of momenta up to about 500 MeV/ c. Furthermore, depending upon the correlations between the directions of the outgoing and of the initial nucleon, the exclusive cross-section turns out to be remarkably sensitive to the shape of the potential binding the nucleons. These correlations also critically affect the domain in the missing energy - missing momentum plane where the exclusive process occurs. Finally the issue of the validity of the semi-classical framework, in leading order of the &ħ expansion, in providing a description of the exclusive processes is shortly addressed.