Question

Define flow velocity in nucleus-nucleus collisions?​

Answer 1

In high energy nucleus nucleus collisions a dense fireball of nuclear matter or even of a quark gluon plasma is created which expands and hadronizes. This collective flow due to the expansion can be concluded on the basisi of kinematics of the final state particles of different masses. Namely it is observed that particles are subject to a common expansion velocity which has some azimuthal anisotropy (called elliptic flow) due to the fact that the created fireball is not spherical as depending on the overlap region of the colliding nuclei

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Answer 2

In high energy nucleus nucleus collisions a dense fireball of nuclear matter or even of a quark gluon plasma is created which expands and hadronizes. This collective flow due to the expansion can be concluded on the basisi of kinematics of the final state particles of different masses. Namely it is observed that particles are subject to a common expansion velocity which has some azimuthal anisotropy (called elliptic flow) due to the fact that the created fireball is not spherical as depending on the overlap region of the colliding nuclei.