Studying the p+Pb ridges using two-particle correlations and cumulants with the ATLAS detector

ATLAS measurements, using two particle correlations and multi particle cumulants, of the relative azimuth ($Deltaphi$) correlations in particle production extending over large pseudorapidity ($eta$) separations (ridge) seen in high multiplicity pPb collisions are presented. The dataset used is $sqrt{s_{NN}} = 5.02$ Tev p+Pb collisions of integrated luminosity about 1 $mu b$. The away side ($Deltaphi sim pi $) ridge in central events (with large energy measured by the forward calorimeter in the Pb fragmentation side, $Sigma E_{t}^{Pb}$) , after subtraction of that in a low $Sigma E_{t}^{Pb}$ event class, is similar in magnitude and $p_{t}$ dependence to the near side ridge ($Deltaphi sim 0$) ridge. The resulting distribution in $Deltaphi$ is consistent with a $cos(2Deltaphi)$ modulation and the magnitude of this modulation ($s_{2}$) shows similar $p_{t}$ dependence as the magnitude of the $cos(2Deltaphi)$ modulation in heavy ion collisions (elliptic flow). The results from Cumulant analysis show similar $p_t$ and $Sigma E_{t}^{Pb}$ dependence for the second order harmonic as obtained from two particle correlations.