Phenomenology of the deuteron electromagnetic form factors

A rigorous extraction of the deuteron charge form factors from tensor polarization data in elastic electron-deuteron scattering, at given values of the 4-momentum transfer, is presented. Then the world data for elastic electron-deuteron scattering is used to parameterize, in three different ways, the three electromagnetic form factors of the deuteron in the 4-momentum transfer range 0-7 fm⁻¹. This procedure is made possible with the advent of recent polarization measurements. The parameterizations allow a phenomenological characterization of the deuteron electromagnetic structure. They can be used to remove ambiguities in the form factors extraction from future polarization data. Received: 28 January 2000 / Revised version: 25 February 2000     

Two-photon exchange effect on deuteron electromagnetic form factors

Corrections of two-photon exchange to proton and neutron electromagnetic form factors are employed to study the effect of two-photon exchange on the deuteron electromagnetic form factors. Numerical results of the effect are given. It is suggested to test the effect in the measurement of Pz$P_z$ in a small angle limit.     

Would the peak value of the electromagnetic quadrupole form factor of the deuteron determine the percentageD-state?

It is shown that short range unitary transformations on the deuteron wave function of the super-soft-core potential of de Tourreil and Sprung, which fix the percentageD state of the deuteronP _D, do not simultaneously fix the peak valueM of the electromagnetic quadrupole form factor of the deuteron within small error bars, even when the transformed wave functions are required to fit the quadrupole moment and the electric form factor of the deuteron within narrow limits. However there is a strong correlation betweenP _D andM ² for realistic interactions whose deuteron wave functions are suppressed at short distances.     

Neutrino disintegration of deuteron and electromagnetic form factos of neutrinos

We consider disintegration of deuteron by low energy neutrinos or antineutrinos due to their electromagnetic form factors. Effects of magnetic or electric dipole moments, electric charge radii and anapole moments of neutrinos are taken into account.     

Contributions to the electromagnetic form factors of the deuteron from isobar configurations

A nonrelativistic calculation of the elastic electron deuteron scattering has been performed in which the effects arising from nucleon polarization have been systematically investigated. These effects have been taken into account by admixing isobar configurations into the deuteron wave function. Explicit expressions for the various contributions to the respective deuteron form factors have been given. At higher momentum transfers inclusion of the isobar configurations leads to a substantial increase in the form factors which qualitatively appears to account for at least some of the discrepancies between theory and experiment.     

On the six-quark structure in the deuteron form factor

The charge and quadrupole deuteron form factors are investigated in a wide region of momentum transfer taking into account the deuteron six quark structure. It is shown that the contribution due to the antisymmetrization of the wave function with respect to quark variables is small and the contribution of the “true” six quark admixtures plays the leading role in the region of large momentum transfer.     

An estimate of two-photon exchange effect on deuteron electromagnetic form factors

The effect of the two-photon exchange on the deuteron electromagnetic form factors is estimated based on an effective Lagrangian approach. A numerical estimate calculation of the effect is discussed. In particular, the effect on the polarization observables is analyzed.     

Isoscalar electromagnetic form factors and the structure of the deuteron at high momentum transfer

We derive general expressions for isoscalar electromagnetic form factors of nuclei including meson-exchange processes such as π, ?, ω and ?πγ exchange. Meson-nucleon vertices for nonzero momentum transfer as well as the effect of the finite width of the ?-meson are taken care of. Specifically, the electromagnetic form factors of the deuteron are calculated up to a momentum transfer of q² ≈ 200 fm^?2. A detailed numerical discussion of the various effects on meson-exchange processes is given. The effect of different deuteron wave functions and two types of photon-nucleon form factors are also discussed.     

An estimate of two-photon exchange effect on deuteron electromagnetic form factors

The effect of the two-photon exchange on the deuteron electromagnetic form factors is estimated based on an effective Lagrangian approach. A numerical estimate calculation of the effect is discussed. In particular, the effect on the polarization observables is analyzed.     

Large-angle pD scattering, the form factor and the NN content of the deuteron

Single scattering and n-exchange are shown to account for all large-q² pD data (k_L 1.5 GeV/c) our to q² 8.5 (GeV/c)². From the extracted body-form factor we predict the deuteron charge form factor which agrees with the recent SLAC data. The agreement invalidates previous estimates of the NN^* content of the neuteron.     

Measurement of the charged pion electromagnetic form factor

Separated longitudinal and transverse structure functions for the reaction 1H(e,e(')pi(+))n were measured in the momentum transfer region Q2 = 0.6--1.6 (GeV/c)(2) at a value of the invariant mass W = 1.95 GeV. New values for the pion charge form factor were extracted from the longitudinal cross section by using a recently developed Regge model. The results indicate that the pion form factor in this region is larger than previously assumed and is consistent with a monopole parametrization fitted to very low Q2 elastic data.     

Parity-violating electron deuteron scattering and the proton's neutral weak axial vector form factor

We report on a new measurement of the parity-violating asymmetry in quasielastic electron scattering from the deuteron at backward angles at Q2=0.038 (GeV/c)2. This quantity provides a determination of the neutral weak axial vector form factor of the nucleon, which can potentially receive large electroweak corrections. The measured asymmetry A=-3.51+/-0.57 (stat)+/-0.58 (syst) ppm is consistent with theoretical predictions. We also report on updated results of the previous experiment at Q2=0.091 (GeV/c)2, which are also consistent with theoretical predictions.     

New short-range electromagnetic current in the deuteron

A new model for short-range isoscalar current in the deuteron and NN system is developed and tested on a variety of isoscalar magnetic observables such as the deuteron magnetic moment, magnetic form factor, and the circular polarization of photons at radiative capture at thermal neutron energies. The model for electromagnetic two-nucleon current proposed in the paper is based on generation of an intermediate dibaryon in the short-range NN interaction. This intermediate dibaryon, in turn, is treated within the new model for intermediate and short-range NN interaction recently proposed by the present authors. The transition current model developed here satisfies the current conservation relation by the construction. Our calculations have demonstrated that the new current model, using only one parameter (with a clear physical meaning), is able to describe, in very good agreement with the experimental data, three basic deuteron observables of magnetic type, viz., the magnetic moment, the photon circular polarization in the process, and the structure function B(Q ²) up to Q ² ≃ 60 fm⁻². The text was submitted by the authors in English.     

QCD constraints for the electromagnetic form factor of the pion

Using the modulus representation, we derive constraints for the behaviour of the electromagnetic form factor of the pion in the time like region [1 GeV², +∞], from information given by perturbative QCD in the space like region [?μ ², ?∞]. A phenomenological μ dependent upper bound for the exponent of the first non leading logarithmic correction is deduced. Restrictions and problems of the method are discussed.