  Results on two-particle angular correlations for charged particles emitted in
pPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV are
presented. The analysis uses two million collisions collected with the CMS
detector at the LHC. The correlations are studied over a broad range of
pseudorapidity, eta, and full azimuth, phi, as a function of charged particle
multiplicity and particle transverse momentum, pt. In high-multiplicity events,
a long-range (2 < abs(Delta(eta)) < 4), near-side (Delta(phi) approximately 0)
structure emerges in the two-particle Delta(eta)-Delta(phi) correlation
functions. This is the first observation of such correlations in proton-nucleus
collisions, resembling the ridge-like correlations seen in high-multiplicity pp
collisions at sqrt(s) = 7 TeV and in AA collisions over a broad range of
center-of-mass energies. The correlation strength exhibits a pronounced maximum
in the range of pt = 1-1.5 GeV and an approximately linear increase with
charged particle multiplicity for high-multiplicity events. These observations
are qualitatively similar to those in pp collisions when selecting the same
observed particle multiplicity, while the overall strength of the correlations
is significantly larger in pPb collisions.
