  We study a phase transition in a non-equilibrium model first introduced in
[5], using the Yang-Lee description of equilibrium phase transitions in terms
of both canonical and grand canonical partition function zeros. The model
consists of two different classes of particles hopping in opposite directions
on a ring. On the complex plane of the diffusion rate we find two regions of
analyticity for the canonical partition function of this model which can be
identified by two different phases. The exact expressions for both distribution
of the canonical partition function zeros and their density are obtained in the
thermodynamic limit. The fact that the model undergoes a second order phase
transition at the critical point is confirmed. We have also obtained the grand
canonical partition function zeros of our model numerically. The similarities
between the phase transition in this model and the Bose-Einstein condensation
has also been studied.
