Study of the long-range azimuthal correlations in $pp$ and $p$+Pb collisions with the ATLAS detector at the LHC

ATLAS measurements 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. The correlations in the "ridge" region are analysed using a new template t method for extraction of ow harmonics. A comparison of this method with the previously used ZYAM method and a detailed study of the dependence of their results on the charged particle multiplicity and the transverse momentum of the particles forming a pair are shown.