Threshold Effects in the Dissociative Recombination Cross Section of HD$^+$ M. Lange$^a$, J. Levin$^a$, U. Hechtfischer$^a$, L. Knoll$^a$, D. Schwalm$^a$, R. Wester$^a$, A. Wolf$^a$, X. Urbain$^c$, and D. Zajfman$^b$ $^a$ Max-Planck-Institut f\"ur Kernphysik and Physikalisches Institut der Universit\"at Heidelberg, D--69029 Heidelberg, Germany $^b$ Department of Particle Physics, Weizmann Institute of Science, Rehovot, 76100, Israel $^c$ D\'epartment de Physique, Universit\'e Catholique de Louvain, Chemin du Cyclotron 2, B1348, Louvain-la-Neuve, Belgium Thresholds are observed in the dissociative recombination rate coefficient of vibrationally cold HD$^+$ in the energy range where new channels H(1s) + D($n$) (or D(1s) + H($n$)) with $n>2$ open. Also, the ion pair production is observed as a sink to the neutral production rate. These thresholds demonstrate that the dissociative recombination cannot be described as a two step process.