Measurement of the ridge correlations in $pp$ and $p$+Pb collisions with the ATLAS detector at the LHC

The ATLAS measurement of azimuthal correlations between particle pairs at large pseudorapidity separation in $pp$ and $p$+Pb collisions are presented. The data were collected using a combination of the minimum-bias and high track-multiplicity triggers. A detailed study of the dependence of two-particle correlations on the charged particle multiplicity, transverse momentum of the pair constituents and the pseudorapidity separation between particles forming a pair is shown. The transverse momentum dependence of a single particle azimuthal anisotropy coefficients, $v_{2} − v_{5}$ in $p$+Pb and $v_{2}$ in $pp$ collisions are also presented. These measurements can help to understand the origin of the long-range correlations seen in high-multiplicity $pp$ and $p$+Pb collisions as well as provide insight into flow phenomena in heavy- ion collisions.