  Measurements from the CMS experiment at the LHC of dihadron correlations for
charged particles produced in PbPb collisions at a nucleon-nucleon
centre-of-mass energy of 2.76 TeV are presented. The results are reported as a
function of the particle transverse momenta (pt) and collision centrality over
a broad range in relative pseudorapidity [Delta(eta)] and the full range of
relative azimuthal angle [Delta(phi)]. The observed two-dimensional correlation
structure in Delta(eta) and Delta(phi) is characterised by a narrow peak at
(Delta(eta), Delta(phi)) approximately (0, 0) from jet-like correlations and a
long-range structure that persists up to at least |Delta(eta)| = 4. An
enhancement of the magnitude of the short-range jet peak is observed with
increasing centrality, especially for particles of pt around 1-2 GeV/c. The
long-range azimuthal dihadron correlations are extensively studied using a
Fourier decomposition analysis. The extracted Fourier coefficients are found to
factorise into a product of single-particle azimuthal anisotropies up to pt
approximately 3-3.5 GeV/c for at least one particle from each pair, except for
the second-order harmonics in the most central PbPb events. Various orders of
the single-particle azimuthal anisotropy harmonics are extracted for associated
particle pt of 1-3 GeV/c, as a function of the trigger particle pt up to 20
GeV/c and over the full centrality range.
