Universal properties of the electromagnetic interactions of spin-one systems.

The dominance of helicity-conserving amplitudes in gauge theory is shown imply universal ratios for the charge, magnetic, and quadrupole form factors spin-one bound states: Gc(Q2) : GM(Q2) : GQ(Q2) = (1 $7) : 2 : -1. These ratios hold at large space-like or time-like momentum transfer in the case of composite systems such as the p or deuteron in &CD. They are also the ratios predicted’for the electromagnetic couplings of the W* for all Q2 in the standard model at tree level. In the case of the deuteron, the leading-twist perturbative QCD predictions are valid at Q2 = jq21 >> AQCDM~, but do not require the kinematical ratio 77 = Q2/4AIj to be large. These results provide new all-angle predictions for the leading power behavior of the tensor polarization Z’2s(Q2, 0) and the invariant ratio B(Q2)/A(Q2). W e a so 1 use a generalization of the Drell-Hearn Gerasimov sum rule to show that the magnetic and quadrupole moment of any composite spin-one system take on the canonical values ,Y = e/M and Q = -e/M2 in the strong binding limit of zero bound-state radius or infinite excitation energy. This allows new empirical constraints on the possible internal structure of the 2’ and W* vector bosons. Simple gauge invariant and covariant models and null zone theory are used to illustrate these results. Complications that arise when the Breit frame is used for form factor analyses are also pointed out. Submitted to Physical Review D * Work supported in part by the Department of Energy under contract number DEAC03-76SF00515.