Electromagnetic moments of relativistic higher spin baryons

We point out a source of ambiguities in the measurements of the electromagnetic moments of spin-3/2 baryons which rely on relativistic Lagrangian models. An anambiguous relation between the parameters of the spin-3/2 electromagnetic Lagrangian and the electromagnetic moments of the spin-3/2 particle exits in general only for on-shell situation, while the measurements are done on ``virtual'' baryons.Comment: 4 pages, 2 figures; contribution to the proceedings of the International Conference on Quark Nuclear Physics (Adelaide, February 2000

New symmetry current for massive spin-3/2 fields

We present several new results which will be of value to theorists working with massive spin-3/2 vector-spinor fields as found, for example, in low and intermediate energy hadron physics and also linearized supergravity. The general lagrangian and propagator for a vector-spinor field in d-dimensions is given. It is shown that the observables of the theory are invariant under a novel continuous symmetry group which is also extended to an algebra. A new technique is developed for exploring the consequences of the symmetry and a previously unknown conserved vector current and charge are found. The current leads to new interactions involving spin-3/2 particles and may have important experimental consequences.Comment: 9 pages, references updated and minor change

Relativistic covariance of quasipotential equations

We argue that most of the relativistic 3-D (quasipotential) equations used in hadron physics are inconsistent with the discrete symmetries like charge conjugation and CPT, yielding an incorrect Lorentz structure for the calculated Green's functions. An exception to this is the equal time approximation to the Bethe-Salpeter equation. We present a covariant quasipotential model for the pion-nucleon interaction based on hadronic degrees of freedom and satisfying the full covariance.Comment: 7 pages, LaTeX (REVTeX), incl. 4 PostScript figure