TY - JOUR
T1 - Harmonic decomposition of two particle angular correlations in Pb–Pb collisions at s vsNN = 2.76 TeV
AU - Aamdt, K.
AU - Bøggild, Hans
AU - Bearden, Ian
AU - Christensen, Christian Holm
AU - Dalsgaard, Hans Hjersing
AU - Gaardhøje, Jens Jørgen
AU - Gulbrandsen, Kristjan Herlache
AU - Nygaard, Casper
AU - Nielsen, Børge Svane
AU - Søgaard, Carsten
PY - 2012/2/28
Y1 - 2012/2/28
N2 - Angular correlations between unidentified charged trigger (t) and associated (a) particles are measured by the ALICE experiment in Pb-Pb collisions at sNN=2.76TeV for transverse momenta 0.25pTa. The shapes of the pair correlation distributions are studied in a variety of collision centrality classes between 0 and 50% of the total hadronic cross section for particles in the pseudorapidity interval |η|<1.0. Distributions in relative azimuth δφ≡φt-φa are analyzed for |δη|≡|ηt-ηa|>0.8, and are referred to as "long-range correlations". Fourier components Vnδ≡〈cos(nδφ)〉 are extracted from the long-range azimuthal correlation functions. If particle pairs are correlated to one another through their individual correlation to a common symmetry plane, then the pair anisotropy Vnδ(pTt,pTa) is fully described in terms of single-particle anisotropies vn(pT) as Vnδ(pTt,pTa)=vn(pTt)vn(pTa). This expectation is tested for 1≤n≤5 by applying a global fit of all Vnδ(pTt,pTa) to obtain the best values vn{GF}(pT). It is found that for 2≤n≤5, the fit agrees well with data up to pTa~3-4GeV/c, with a trend of increasing deviation as pTt and pTa are increased or as collisions become more peripheral. This suggests that no pair correlation harmonic can be described over the full 0.25T<15GeV/c range using a single vn(pT) curve; such a description is however approximately possible for 2≤n≤5 when pTa<4GeV/c. For the n=1 harmonic, however, a single v1(pT) curve is not obtained even within the reduced range pTa<4GeV/c.
AB - Angular correlations between unidentified charged trigger (t) and associated (a) particles are measured by the ALICE experiment in Pb-Pb collisions at sNN=2.76TeV for transverse momenta 0.25pTa. The shapes of the pair correlation distributions are studied in a variety of collision centrality classes between 0 and 50% of the total hadronic cross section for particles in the pseudorapidity interval |η|<1.0. Distributions in relative azimuth δφ≡φt-φa are analyzed for |δη|≡|ηt-ηa|>0.8, and are referred to as "long-range correlations". Fourier components Vnδ≡〈cos(nδφ)〉 are extracted from the long-range azimuthal correlation functions. If particle pairs are correlated to one another through their individual correlation to a common symmetry plane, then the pair anisotropy Vnδ(pTt,pTa) is fully described in terms of single-particle anisotropies vn(pT) as Vnδ(pTt,pTa)=vn(pTt)vn(pTa). This expectation is tested for 1≤n≤5 by applying a global fit of all Vnδ(pTt,pTa) to obtain the best values vn{GF}(pT). It is found that for 2≤n≤5, the fit agrees well with data up to pTa~3-4GeV/c, with a trend of increasing deviation as pTt and pTa are increased or as collisions become more peripheral. This suggests that no pair correlation harmonic can be described over the full 0.25T<15GeV/c range using a single vn(pT) curve; such a description is however approximately possible for 2≤n≤5 when pTa<4GeV/c. For the n=1 harmonic, however, a single v1(pT) curve is not obtained even within the reduced range pTa<4GeV/c.
M3 - Journal article
SN - 0370-2693
VL - 708
SP - 249
EP - 264
JO - Physics Letters B: Particle Physics, Nuclear Physics and Cosmology
JF - Physics Letters B: Particle Physics, Nuclear Physics and Cosmology
IS - 3-5
ER -