The trajectories of six representative particles that attain Lorentz factors γ > 30 in the simulation S2K025 (left panel), and the evolution of the Lorentz factor as a function of coordinate z (right panel). The dashed line indicates the center of the current sheet. Note that many of the particles start at z ≈ 12.5 λ _p and close to the center of the current sheet; this is the location of the large X-line on the lower left in Figure 8. The crosses indicate the particle position at the beginning of the acceleration phase.