Azimuthal Dependence of the Fractional Parton Energy Loss in Cu + Au Collisions at $$\sqrt {{{s}_{{NN}}}} $$ = 200 GeV

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.