Illustration: Carin Cain

Figure 3: Geometry of a high-energy heavy-ion collision. The left panel shows the collision of two Lorentz-contracted gold nuclei: the radius of the gold nuclei, $RAu$, is contracted by $γ$ in the direction of motion $z$. The right panel shows the same collision viewed from a direction that is perpendicular to the motion. The impact parameter, $b$, is along the $x$ axis, and the remaining transverse direction is the $y$ axis.