Three and Two Hadron Correlations in $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$ Proton-Proton and Nucleus-Nucleus Collisions

We compare the azimuthal correlations arising from three and two hadron production in $p+p$ and $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$. We show that in $\mathrm{Au}+\mathrm{Au}$, the two away side partons in two-to-three processes have in average a smaller and a greater path length than the average path length of the away-side parton in two-to-two processes. Since in average the particle with the shortest path length in two-to-three processes loses less energy, with respect to the away-side particle in two-to-two processes, this effect leads to a relative enhancement of the ratio of two-to-three to two-to-two processes in $\mathrm{Au}+\mathrm{Au}$ compared to $p+p$ collisions. We argue that this phenomenon may be responsible for the shape of the away side in azimuthal correlations at the Relativistic Heavy-Ion Collider.

Figure 1

Comparison of the differential cross sections for two-to-two (full circles) and two-to-three (open circles) processes in $p+p$ (left panel) and $A+A$ (right panel) collisions.

Figure 2

Distribution of path lengths for two-to-two and two-to-three processes for the away-side partons, obtained by discarding the shortest of the path lengths in each case.