transverse view. longitudinal view. A sketch of the geometry of a non-central heavy-ion collision in the \subref{fig1a} transverse $(x_{\mathrm{RP}},y)$ and \subref{fig1b} reaction $(x_{\mathrm{RP}},z)$ planes The $x_{\mathrm{RP}}$ axis points along the direction of the impact parameter given by the distance between the centers of the colliding nuclei, while the $z$ axis is oriented along the direction of the colliding nuclei The full (open) circles represent the protons (neutrons) from projectile (red) and target (blue) nuclei The participant nucleons are shown in purple In panel~\subref{fig1a}, the arrows indicate the eccentricity vectors ($\epsilon_n$ is shown as example) and corresponding reaction (\PsiRP), projectile/target spectator ($\Psi_\mathrm{SP}^{\rm P,T}$), and participant (multiple \PsiPP, $n\ge1$) plane angles Panel \subref{fig1b} shows the outward deflection, indicated by curved arrows, of the spectators and fragmentation products of the projectile ($\eta>0$) and target ($\eta0$) recoil nuclei, such as protons ($p$), neutrons ($n$), and nuclei (deuteron, helium, etc).