Onset of the ridge structure in $AA,pA$, and $pp$ collisions

It is shown that the anomalous sharp increasing of the strength of the near-side ridge structures observed in Au-Au collisions at $\sqrt{s}=62$ and $\sqrt{s}=200$ GeV and the onset of the ridge structure in $p\text{Pb}$ and in $pp$ collisions can be naturally explained in the framework of string percolation. In all the cases the near-side strength reflects the collision area covered by the strings stretched between the colliding objects and therefore it is related to the shape of their profile functions. The dependence of the pseudorapidity and azimuthal widths on multiplicity and energy is qualitatively explained.

Figure 1

String density $\rho$ plotted as a function of $N_{\mathrm{ch}}$ for Au-Au collisions at $\sqrt{s}=200$ GeV.

Figure 2

Comparison between our results on the strength of the near-side ridge for Au-Au collisions at two RHIC energies $\sqrt{s}=200$ GeV (upper red line) and $\sqrt{s}=62$ GeV (lower blue line) with experimental data [28] in terms of $N_{\mathrm{ch}}$.

Figure 3

Comparison between our results on the strength of the near-side ridge for $pp$ collisions at $\sqrt{s}=7$ TeV (lower blue line) and $p\text{Pb}$ collisions $\sqrt{s}=5.02$ TeV (upper red line) with experimental data [9] versus $N_{\mathrm{ch}}$.

Figure 4

Pseudorapidity width of the near-side ridge for Au-Au collisions at two RHIC energies $\sqrt{s}=200$ GeV and $\sqrt{s}=62$ GeV [28] plotted as a function of $\rho$. Curves obtained from Eq. (7) for Au-Au collisions at $\sqrt{s}=200$ GeV (lower red) and $\sqrt{s}=62$ GeV (upper blue).

Figure 5

Azimuthal width of the near-side ridge for Au-Au collisions at $\sqrt{s}=200$ and $\sqrt{s}=62$ GeV [28] versus $\rho$. Curves were obtained from Eq. (14) for Au-Au collisions at $\sqrt{s}=200$ GeV (lower red) and $\sqrt{s}=62$ GeV (upper blue).