  In this paper we explore the entanglement of two relativistic spin-$1/2$
particles with continuous momenta. The spin state is described by the Bell
state and the momenta are given by Gaussian distributions of product form.
Transformations of the spins are systematically investigated in different boost
scenarios by calculating the orbits and concurrence of the spin degree of
freedom. By visualizing the behavior of the spin state we get further insight
into how and why the entanglement changes in different boost situations.
