Charge conjugation invariance of the Spectator Equations

In response to recent critcism, we show how to define the spectator equations for negative energies so that charge conjugation invariance is preserved. The result, which emerges naturally from the application of spectator principles to systems of particles with negative energies, is to replace all factors of the external energies $W_i$ by $\sqrt{W^2_i}$, insuring that the amplitudes are independent of the sign of the energies $W_i$.Comment: 10 pages; 4 figure

Relativistic Theory of Few-Body Systems

Very significant advances have been made in the relativistic theory of few body systems since I visited Peter Sauer and his group in Hannover in 1983. This talk provides an opportunity to review the progress in this field since then. Different methods for the realtivistic calculation of few nucleon systems are briefly described. As an example, seven relativistic calculations of the deuteron elastic structure functions, $A$, $B$, and $T_{20}$, are compared. The covariant spectator theory, among the more successful and complete of these methods, is described in more detail.Comment: 13 pages, 4 figures, Invited talk to the 2002 CFIF Fall Workshop on Nuclear Dynamics: From Quarks to Nuclei (in honor of Peter Sauer) 31 Oct - 2 Nov 2002, Lisbon, Portuga

Extraction of the Ratio of the Neutron to Proton Structure Functions from Deep Inelastic Scattering

We study the nuclear ($A$) dependence of the European Muon Collaboration (EMC) effect at high values of $x$ ($x \geq 0.6$). Our approach makes use of conventional nuclear degrees of freedom within the Relativistic Impulse Approximation. By performing a non-relativistic series expansion we demonstrate that relativistic corrections make a substantial contribution to the effect at $x \gtrsim 0.6$ and show that the ratio of neutron to proton structure functions extracted from a global fit to all nuclei is not inconsistent with values obtained from the deuteron.Comment: 12 pages, 2 figures available upon request, Revte

The deuteron: a mini-review

We review some recent results for elastic electron deuteron scattering (deuteron form factors) and photodisintegration of the deuteron, with emphasis on the recent high energy data from Jefferson Laboratory (JLab).Comment: 14 pages, 11 figures, Invited talk given to the Conference on Mesons & Light Nuclei, held in Prague, Czech Republic, July 2- 6, 200

Electromagnetic structure of the deuteron

Recent measurements of the deuteron electromagnetic structure functions A, B, and $T_{20}$ extracted from high energy elastic $ed$ scattering, and the cross sections and asymmetries extracted from high energy photodisintegration $\gamma+d\to n+p$, are reviewed and compared to theory. The theoretical calculations range from nonrelativistic and relativistic models using the traditional meson and baryon degrees of freedom, to effective field theories, to models based on the underlying quark and gluon degrees of freedom of QCD, including nonperturbative quark cluster models and perturbative QCD. We review what has been learned from these experiments, and discuss why elastic $ed$ scattering and photodisintegration seem to require very different theoretical approaches, even though they are closely related experimentally.Comment: review paper; 93 pages, 35 figure

A Comment on General Formulae for Polarization Observables in Deuteron Electrodisintegration and Linear Relations

We establish a simple, explicit relation between the formalisms employed in the treatments of polarization observables in deuteron two-body electrodisintegration published by Arenh\"ovel, Leidemann, and Tomusiak in Few-Body Systems {\bf 15}, 109 (1993) and the results of the present authors published in Phys.~Rev.~C {\bf 40}, 2479 (1989). We comment on the overlap between the two sets of results.Comment: 9 pages, no figure

Covariant spectator theory of np scattering: Deuteron quadrupole moment

The deuteron quadrupole moment is calculated using two covariant spectator theory model wave functions obtained from the 2007 high-precision fits to np scattering data. Included in the calculation are a new class of isoscalar np interaction currents automatically generated by the nuclear force model used in these fits. The prediction for model WJC-1, with larger relativistic P-state components, is 2.5% smaller than the experimental result, in common with the inability of models prior to 2014 to predict this important quantity. However, model WJC-2, with very small P-state components, gives agreement to better than 1%, similar to the results obtained recently from chiral effective field theory predictions to next-to-next-to-next-to-leading order

Spin and angular momentum in the nucleon

Using the covariant spectator theory (CST), we present the results of a valence quark-diquark model calculation of the nucleon structure function f(x) measured in unpolarized deep inelastic scattering (DIS), and the structure functions g1(x) and g2(x) measured in DIS using polarized beams and targets. Parameters of the wave functions are adjusted to fit all the data. The fit fixes both the shape of the wave functions and the relative strength of each component. Two solutions are found that fit f(x) and g1(x), but only one of these gives a good description of g2(x). This fit requires the nucleon CST wave functions contain a large D-wave component (about 35%) and a small P-wave component (about 0.6%). The significance of these results is discussed.Comment: 27 pages; 13 figure