Polarization transfer in elastic electron scattering from nucleons and deuterons

Abstract

We present a description, including relevant formulas and numerical estimates, of a set of polarization transfer experiments which appear to offer a feasible way to separate the deuteron charge and quadrupole form factors and measure the neutron and proton electric form factors. The experiments require a 2 to 4 GeV high-intensity, highduty factor, longitudinally polarized electron beam and require that the polarization of the recoiling hadron be measured in a second, analyzing, scattering. The relevant asymmetries are fairly large, and our calculations show that they are sensitive to different models obtained from existing data. Attention is called to the fact that the proposed deuteron measurements will require new 10% measurements of vector and tensor analyzing powers of deuterons with kinetic energy from 150 to 450 MeV. NUCLEAR STRUCTURE Analysis of electron polarization transfer experiments to measure Gz&, oz", separate d monopole and quadrupole form factors.

Nucleon electromagnetic form factors

“…In 1969, in a review paper Dombey [Dom69] also discussed the virtues of measuring polarization observables in elastic and inelastic lepton scattering; however his emphasis was to do these measurements with a polarized lepton on a polarized target. Furthermore in 1982 Arnold, Carlson and Gross [Arn81]emphasized that the best way to measure the electric FF of the neutron would be to use the 2 H( e, e ′ n)p reaction. Both a polarized target, and a focal plane polarimeter (to measure recoil polarization), have been used to obtain nucleon FFs.…”

Hadron structure at lowQ2

“…Such an experiment requires a polarized electron beam and a polarized target, or equivalently the measurement of the nucleon's polarization in the final state. The measured asymmetry takes the form (Arnold et al, 1981) …”

The neutron electric form factor to Q² = 1.45 (GeV/c)²

“…As noted earlier, Dombey [158] stated that the formalism for recoil polarization was identical to that for target polarization; however, details were not provided. The first detailed results were reported by Akhiezer and Rekalo [159] and Arnold, Carlson, and Gross [160]. Below, we follow the pedagogical overview of the recoil polarimetry 107 technique given by Arenh6vel, Leidemann, and Tomusiak [166].…”

“…Akhiezer and Rekalo demonstrated that, in the one-photon exchange approximation, the polarization of the recoil nucleon is confined to the scattering plane, and the component that is perpendicular (parallel) to the recoil nucleon's three-momentum (i.e., to q) is proportional to GEGM (G'). In an extension of Akhiezer and Rekalo's initial work, in a seminal paper in 1981, Arnold, Carlson, and Gross [160] proposed that a measurement of the recoil neutron's polarization in quasielastic polarized-electron, unpolarized-deuteron scattering via a secondary, analyzing, reaction appeared to be a straightforward, albeit challenging, method for a precision measurement of the experimentally elusive neutron electric form factor.…”

“…Indeed, Arnold, Carlson, and Gross [160] specifically suggested that a secondary scattering from unpolarized protons should be employed as the analyzing reaction as the analyzing powers for pp and np scattering are large and well known. To illustrate Without such a magnetic field, the up-down scattering asymmetry is only sensitive instead, such a magnetic field is available and the polarization is precessed in the k-i plane through an angle X (as indicated schematically in Fig.…”