Measurement of the azimuthal anisotropy coefficient v2 for the emission of α particles in nucleus-nucleus collisions at energies 1.88–10.6 GeV/nucleon

The azimuthal anisotropy of the emission of α particles in collisions of the ²²Ne, ²⁴Mg, ⁵⁶Fe, and ¹⁹⁷Au nuclei with photoemulsion nuclei has been measured at projectile energies E _pr = 1.88–10.6 GeV/nucleon. The results are compared with similar measurements for protons. It has been found that the ratio of the azimuthal anisotropy coefficients v ₂ for α particles and protons is equal to 6 ± 2 at low energies E _pr ≈ 2 GeV/nucleon, whereas these coefficients coincide with each other for energies E _pr ≥ 4 GeV/nucleon. This difference may indicate that, at low projectile energies, α particles are formed predominantly at the early stage of a collective flow. Formation of α particles for E _pr ≥ 4 GeV/nucleon likely occurs at the stage of nuclear matter scattering.