Measurement of long-range pseudorapidity correlations and azimuthal harmonics in √sNN= 5.02 TeV proton-lead collisions with the ATLAS detector

Measurements of two-particle correlation functions and the first five azimuthal harmonics, v1 to v5, are presented, using 28 nb^−1 of p+Pb collisions at a nucleon-nucleon center-of-mass energy of√sNN =5.02 TeV measured with the ATLAS detector at the LHC. Significant long-range “ridgelike” correlations are observed for pairs with small relative azimuthal angle (|Deltaφ| < π/3) and back-to-back pairs (|Deltaφ| > 2π/3) over the transverse momentum range 0.4 4 GeV. The v2(pT), v3(pT), and v4(pT) are compared to the vn coefficients in Pb+Pb collisions at √sNN =2.76 TeV with similar event multiplicities. Reasonable agreement is observed after accounting for the difference in the average pT of particles produced in the two collision systems.