Transverse cuts (in the x − z plane) of the distribution of the Lorentz factor at three different positions along the jet for case B at t = 25 000 when the jet head reaches y = 600. The positions of the three cuts correspond to the three red arrows in Fig. 5. Top-left panel: y = 100, the bottom-left panel is at y = 300, and the right panel is at y = 450. We remark that the two left panels cover a square with −4 ≤ x, z ≤ 4, while the right panel covers −8 ≤ x, z ≤ 8; moreover, in the two left panels, the maximum γ is 10, while in the right panel the maximum γ is 5.