Non Intercommuting Configurations in the Collisions of Type-I $U(1)$   Cosmic Strings
  It is shown that for small relative angle and kinetic energy two type I $U(1)$ strings can form bound states upon collision instead of the more familiar intercommuting configuration. The velocity below which this may happen is estimated as function of the ratio of the coupling constants in the theory, crossing angle and initial kinetic energy. 
L. M. A. Bettencourt and T. W. B. Kibble