A study of the anisotropy associated with dipole asymmetry in heavy ion collisions

The anisotropy associated with the initial dipole asymmetry in heavy ion collisions is studied via the two-particle relative azimuthal angle (Δφ = φ^a - φ^b) correlations, within a multi-phase transport model. For a broad selection of centrality, transverse momenta () and pseudorapidity (η^{a, b}), a fitting method is used to decompose the anisotropy into a rapidity-even component, characterized by the Fourier coefficient v₁, and a global momentum conservation component. The extracted v₁ values are negative for p_T ≲ 0.7-0.9 GeV, reach a maximum at 2-3 GeV, and decrease at higher p _T. The v₁ values vary weakly with η and centrality, but increase with collision energy and the parton cross-section. The extracted global momentum conservation component is found to depend on Δη = η^a - η^b for |Δη| < 3.