The separation of the three form factors (charge monopole, charge
quadrupole and magnetic dipole) in elastic scattering from deuterium
represents qualitatively new information which is unavailable in the
absence of polarization observables. Measurement of the tensor
polarization have been made at MIT/Bates [Ga94a] and
Novosibirsk [Jopc][Gi90] for momentum transfers up to about
1 (GeV/c)
. The node in the monopole form factor
results, in
impulse approximation, from the short-range repulsion in the NN
interaction which produces a zero in the radial wavefunction. When
additional dynamical input is included, this node reflects a cancellation
among amplitudes, making the location of this minimum quite sensitive to
the assumed input. Figure
shows the experimental data along
with non-relativistic and relativistic calculations. Note that a naive
interpretation would be that the data seem to favor the absence of
exchange currents. This is in distinction to the situation for the
isoscalar A=3 form factor. It has recently been shown that, in the context
of non-relativistic theory, there is a correlation, indeed, a linear
relationship, between the position of the minimum in the isoscalar charge
form factors for A=2 and A=3 [He94]. This line does not pass
through the experimental data. To say this another way, agreement with
one system can only be achieved at the expense of agreement with the
other. Given the somewhat similar physics of A=2 and A=3 this situation
is, at the moment, rather perplexing and argues strongly for a more
precise experimental location of the minimum in .
