Azimuthal Asymmetry of Pion-Meson Emission around the Projectile and Target Sides in Au+Au Collision at 1A GeV 后印本

摘要: The ratio of the number of emitted pions from the target side to that from the projectile side at target rapidity
within the reaction plane is investigated for the study of the pion dynamics with an isospin-dependent quantum
molecular dynamic model. The results show that high-energy pions are emitted preferentially towards the target
side and, therefore, they are freezed out at the early stage of the collision. By contrast, low-energy pions
are emitted predominantly in the opposite direction, which means that they are emitted in later stage. This
arguement is based on the shadowing effect caused by the interaction of pions with the spectator matter in
peripheral collisions at target or projectile rapidities. This phenomenon disappears in the central collision or at
midrapidity due to the weaker shadowing effect. The calculated ratios are also compared with the experimental
data.