The hoop conjecture is well confirmed in momentarily static spaces, but it has not been investigated systematically for the system with relativistic motion. To test the hoop conjecture for non-time-symmetric initial data, we consider the initial data of two colliding black holes with momentum and search an apparent horizon that encloses two black holes. In testing the hoop conjecture, we use two definitions of gravitational mass: one is the Arnowitt-Deser-Misner (ADM) mass and the other is the quasilocal mass defined by Hawking. Although both definitions of gravitational mass give a fairly consistent picture of the hoop conjecture, the hoop conjecture with the Hawking mass can judge the existence of an apparent horizon for a wider range of parameters of the initial data compared to the ADM mass.

• Received 5 September 2001

DOI:https://doi.org/10.1103/PhysRevD.65.064034