Azimuthal Anisotropy and Correlations at Large Transverse Momenta in $p+p$ and $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ Collisions at $\sqrt{s_{NN}}=200\mathrm{G}\mathrm{e}\mathrm{V}$

Results on high transverse momentum charged particle emission with respect to the reaction plane are presented for $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions at $\sqrt{s_{NN}}=200\mathrm{G}\mathrm{e}\mathrm{V}$. Two- and four-particle correlations results are presented as well as a comparison of azimuthal correlations in $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions to those in $p+p$ at the same energy. The elliptic anisotropy $v_2$ is found to reach its maximum at $p_t\sim 3\mathrm{G}\mathrm{e}\mathrm{V}/c$, then decrease slowly and remain significant up to $p_t\approx 7–10\mathrm{G}\mathrm{e}\mathrm{V}/c$. Stronger suppression is found in the back-to-back high-$p_t$ particle correlations for particles emitted out of plane compared to those emitted in plane. The centrality dependence of $v_2$ at intermediate $p_t$ is compared to simple models based on jet quenching.

Figure 1

Azimuthal correlations in $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions (squares) as a function of centrality (peripheral to central from left to right) compared to minimum bias azimuthal correlations in $p+p$ collisions (circles). Errors are statistical only.

Figure 2

$v_2$ of charged particles as a function of transverse momentum from the two-particle cumulant method (triangles) and four-particle cumulant method (stars). Open circles show the two-particle correlation results after subtracting the correlations measured in $p+p$ collisions. Only statistical errors are shown.

Figure 3

Upper panel: Azimuthal distributions of associated particles for trigger particles in plane (squares) and out of plane (triangles) for $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions at centrality 20%–60%. Open symbols are reflections of solid symbols around $\Delta \varphi =0$ and $\Delta \varphi =\pi$. Elliptic flow contribution is shown by dashed lines. Lower panel: Distributions after substracting elliptic flow, and the corresponding measurement in $p+p$ collisions (histogram).

Figure 4

$v_2$ at $3\le p_t\le 6\mathrm{G}\mathrm{e}\mathrm{V}/c$ versus impact parameter, $b$, compared to models of particle emission by a static source (see text).