Electrons
and Mirror Symmetry
The neutral weak force
between an electron and a target particle, mediated by the Z boson, can be
isolated by measuring the fractional change under a mirror reflection of the
scattering probability of relativistic longitudinally polarized electrons off
unpolarized targets. This technique yields neutral weak force measurements at a
length scale of 1 femtometer, in contrast to high energy collider measurements
that probe much smaller length scales. Study of the variation of the weak force
over a range of length scales provides a stringent test of theory,
complementing collider measurements. We describe a recent measurement of the
neutral weak force between two electrons by the E158 experiment at the Stanford
Linear Accelerator Center. While the
weak force between an electron and positron has been extensively studied, that
between two electrons had never directly been measured. We conclude by
discussing prospects for even more precise measurements at future facilities.