Scaling of Anisotropic Flow and Momentum-Space Densities for Light   Particles in Intermediate Energy Heavy Ion Collisions
  Anisotropic flows ($v_2$ and $v_4$) of light nuclear clusters are studied by Isospin-Dependent Quantum Molecular Dynamics model for the system of $^{86}$Kr + $^{124}$Sn at intermediate energy and large impact parameters. Number-of-nucleon scaling of the elliptic flow ($v_2$) are demonstrated for the light fragments up to $A$ = 4, and the ratio of $v_4/v_2^2$ shows a constant value of 1/2. In addition, the momentum-space densities of different clusters are also surveyed as functions of transverse momentum, in-plane transverse momentum and azimuth angle relative to the reaction plane. The results can be essentially described by momentum-space power law. All the above phenomena indicate that there exists a number-of-nucleon scaling for both anisotropic flow and momentum-space densities for light clusters, which can be understood by the coalescence mechanism in nucleonic degree of freedom for the cluster formation. 
T. Z. Yan, Y. G. Ma, X. Z. Cai, J. G. Chen, D. Q. Fang, W. Guo, C. W.   Ma, E. J. Ma, W. Q. Shen, W. D. Tian, K. Wang