Abstract
The properties of the quark-gluon medium formed in Cu + Au collisions at an energy of \(\sqrt {{{s}_{{NN}}}} \) = 200 GeV can be investigated using information on the energy loss of high-energy partons ( \({{p}_{{\text{T}}}} \gg {{\Lambda }_{{{\text{QCD}}}}}\) ). One of the quantities that can be estimated experimentally is the fractional parton energy loss \({{S}_{{{\text{loss}}}}}\) . On the basis of the data on the elliptic flow \({{v}_{2}}\) of \({{\pi }^{0}}\) mesons at high \({{p}_{{\text{T}}}}\) , azimuthal dependences of the fractional parton energy loss \({{S}_{{{\text{loss}}}}}(\Delta \varphi )\) are obtained, and dependences of the energy loss on the effective parton path length \({{S}_{{{\text{loss}}}}}({{L}_{{{\text{eff}}}}})\) 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 \({{\pi }^{0}}\) -meson emission relative to the reaction plane \({{\Delta E} \mathord{\left/ {\vphantom {{\Delta E} {{{L}_{{{\text{eff}}}}}(\Delta \varphi )}}} \right. \kern-0em} {{{L}_{{{\text{eff}}}}}(\Delta \varphi )}}\) are also presented.
