Research Papers in Physics and Astronomy


Date of this Version



JHEP09 (2010) 091


Open access



Results on two-particle angular correlations for charged particles emitted in proton-proton collisions at center-of-mass energies of 0.9, 2.36, and 7TeV are presented, using data collected with the CMS detector over a broad range of pseudorapidity (n) and azimuthal angle (?). Short-range correlations in [?]n, which are studied in minimum bias events, are characterized using a simple \independent cluster" parametrization in order to quantify their strength (cluster size) and their extent in n (cluster decay width). Long-range azimuthal correlations are studied differentially as a function of charged particle multiplicity and particle transverse momentum using a 980 nb-1 data set at 7TeV. In high multiplicity events, a pronounced structure emerges in the two-dimensional correlation function for particle pairs with intermediate pT of 1-3 GeV/c, 2.0 < |[?]n| < 4.8 and [?][?] [?]0. This is the first observation of such a long-range, near-side feature in two-particle correlation functions in pp or pp collisions.