  We report on simulations of the first order phase transition in YBCO using
the Lawrence-Doniach model. We find that the magnetization discontinuity
vanishes and the first order transition line ends at a critical end point for
low magnetic fields in agreement with experiment. The transition is not
associated with vortex lattice melting, but separates two vortex liquid states
characterized by different degrees of short-range crystalline order and
different length scales of correlations between vortices in different layers.
