Measurement of the elliptic flux of Z {>=} 2 charged particles in collisions of relativistic nuclei with photoemulsion nuclei

The azimuthal asymmetry is measured for the emission of Z ≥ 2 particles from the interaction of 22Ne, 24Mg, 32S, 56Fe, 197Au, and 207Pb nuclei with photoemulsion nuclei that is induced by semicentral collisions characterized by projectile energies in the range E pr = 1.88–200 GeV per nucleon and by impact-parameter (b) values in the range 0.12 ≤ b/b max ≤ 0.70. The results of these measurements are compared with the results of similar measurements for protons. It is found that, at a low energy of E pr ≈ 2 GeV per nucleon, the ratio of the azimuthal-anisotropy coefficients v 2 for Z ≥ 2 particles and protons is 6 ± 2, but that, for energies in the region E pr ≥ 4 GeV per nucleon, the coefficients in question agree with each other. This may suggest that, at low energies, Z ≥ 2 particles are predominantly formed at an early stage of the development of a collective flow. For E pr ≥ 4 GeV per nucleon, these particles are presumably formed at the stage of nuclear-matter expansion. Other possible explanations for the results of the observation of an elliptic flux of Z ≥ 2 particles are discussed.