Azimuthal Dependence of the Fractional Parton Energy Loss in Cu + Au Collisions at √ s_NN = 200 GeV

The properties of the quark-gluon medium formed in Cu + Au collisions at an energy of √ s_NN = 200 GeV can be investigated using information on the energy loss of high-energy partons ( p_T Λ _QCD ). One of the quantities that can be estimated experimentally is the fractional parton energy loss S_loss . On the basis of the data on the elliptic flow v₂ of π ⁰ mesons at high p_T , azimuthal dependences of the fractional parton energy loss S_loss(Δ φ ) are obtained, and dependences of the energy loss on the effective parton path length S_loss(L_eff) are constructed by considering the azimuthal distribution of the color charge density. Estimates of the effective medium stopping power as a function of the azimuthal angle of π ⁰ -meson emission relative to the reaction plane Δ E / Δ E L_eff(Δ φ ) . -0em L_eff(Δ φ ) are also presented.