  Almost all of the $>600$ known Kuiper belt objects (KBOs) have been
discovered within 50 AU of the Sun. One possible explanation for the observed
lack of KBOs beyond 50 AU is that the distant Kuiper belt is dynamically very
cold, and thus thin enough on the sky to have slipped between previous deep
survey fields. We have completed a survey designed to search for a dynamically
cold distant Kuiper belt near the invariable plane of the Solar system. In $2.3
{\rm deg}^2$ we have discovered a total of 33 KBOs and 1 Centaur, but no
objects in circular orbits beyond 50 AU. We find that we can exclude at 95% CL
the existence of a distant disk inclined by $i\le1\arcdeg$ to the invariable
plane and containing more than 1.2 times as many $D>185$ km KBOs between 50 and
60 AU as the observed inner Kuiper belt, if the distant disk is thinner than
$\sigma=1\fdg75$.
