Measurements of two-particle correlation functions and the first five
azimuthal harmonics, v1β to v5β, are presented, using 28 nbβ1
of p+Pb collisions at a nucleon-nucleon center-of-mass energy of
sNNββ=5.02 TeV measured with the ATLAS detector at the LHC.
Significant long-range ``ridge-like'' correlations are observed for pairs with
small relative azimuthal angle (β£ΞΟβ£<Ο/3) and back-to-back pairs
(β£ΞΟβ£>2Ο/3) over the transverse momentum range 0.4<pTβ<12
GeV and in different intervals of event activity. The event activity is defined
by either the number of reconstructed tracks or the total transverse energy on
the Pb-fragmentation side. The azimuthal structure of such long-range
correlations is Fourier decomposed to obtain the harmonics vnβ as a function
of pTβ and event activity. The extracted vnβ values for n=2 to 5
decrease with n. The v2β and v3β values are found to be positive in the
measured pTβ range. The v1β is also measured as a function of pTβ and is observed to change sign around pTββ1.5β2.0 GeV and
then increase to about 0.1 for pTβ>4 GeV. The v2β(pTβ),
v3β(pTβ) and v4β(pTβ) are compared to the vnβ coefficients in
Pb+Pb collisions at sNNββ=2.76 TeV with similar event
multiplicities. Reasonable agreement is observed after accounting for the
difference in the average pTβ of particles produced in the two
collision systems.Comment: 21 pages plus author list + cover pages (34 pages total), 16 figures,
submitted to Phys. Rev. C., All figures including auxiliary figures can be
found at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2013-04