  The anisotropy of the azimuthal distributions of charged particles produced
in PbPb collisions with a nucleon-nucleon center-of-mass energy of 2.76 TeV is
studied with the CMS experiment at the LHC. The elliptic anisotropy parameter
defined as the second coefficient in a Fourier expansion of the particle
invariant yields, is extracted using the event-plane method, two- and
four-particle cumulants, and Lee--Yang zeros. The anisotropy is presented as a
function of transverse momentum (pt), pseudorapidity (eta) over a broad
kinematic range: 0.3 < pt < 20 GeV, abs(eta) < 2.4, and in 12 classes of
collision centrality from 0 to 80%. The results are compared to those obtained
at lower center-of-mass energies, and various scaling behaviors are examined.
When scaled by the geometric eccentricity of the collision zone, the elliptic
anisotropy is found to obey a universal scaling with the transverse particle
density for different collision systems and center-of-mass energies.
