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 ~ { } { 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 \leq 1 \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 \fdg 75 .