BARC/PUB/2012/0900

 
 

Centrality dependence of dihadron correlations and azimuthal anisotropy harmonics in PbPb collisions at √sNN=2.76 TeV

 
     
 
Author(s)

Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.; Choudhury, R. K.; Dutta, D.; Kailas, S.; Kumar, V.; Mohanty, A. K.; Pant, L. M.; Shukla, P.; and others
(NPD)

Source

European Physical Journal-C, 2012. Vol. 72 (5): pp. 2012

ABSTRACT

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 (Δη) and the full range of relative azimuthal angle (Δφ). The observed two-dimensional correlation structure in Δη and Δφ is characterised by a narrow peak at (Δη,Δφ) ≈ (0, 0) from jet-like correlations and a longrange structure that persists up to at least |Δη| = 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 dihedron 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 ≈ 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.

 
 
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