Abstract
ATLAS measurements of two-particle correlations are presented for ís=5.02 and 13 TeV pp collisions and for ísNN=5.02 TeV p+Pb collisions at the LHC. The correlation functions are measured as a function of relative azimuthal angle __, and pseudorapidity separation __, using charged particles detected within the pseudorapidity interval |_|2, is studied using a template fitting procedure to remove a back-to-back contribution to the correlation function that primarily arises from hard-scattering processes. In addition to the elliptic, cos(2__), modulation observed in a previous measurement, the pp correlation functions exhibit significant cos(3__) and cos(4__) modulation. The Fourier coefficients vn,n associated with the cos(n__) modulation of the correlation functions for n=2_4 are measured as a function of charged-particle multiplicity and charged-particle transverse momentum. The Fourier coefficients are observed to be compatible with cos(n_) modulation of per-event single-particle azimuthal angle distributions. The single-particle Fourier coefficients vn are measured as a function of charged-particle multiplicity, and charged-particle transverse momentum for n=2_4. The integrated luminosities used in this analysis are, 64 nb_1 for the ís=13 TeV pp data, 170 nb_1 for the ís=5.02 TeV pp data, and 28 nb_1 for the ísNN=5.02 TeV p+Pb data.