Elsevier

Physics Letters B

Volume 708, Issues 3–5, 28 February 2012, Pages 249-264
Physics Letters B

Harmonic decomposition of two particle angular correlations in Pb–Pb collisions at sNN=2.76TeV

https://doi.org/10.1016/j.physletb.2012.01.060Get rights and content
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open access

Abstract

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 0.25<pTt,a<15GeV/c, where pTt>pTa. 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 Δϕϕtϕa are analyzed for |Δη||ηtηa|>0.8, and are referred to as “long-range correlations”. Fourier components VnΔcos(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 1n5 by applying a global fit of all VnΔ(pTt,pTa) to obtain the best values vn{GF}(pT). It is found that for 2n5, the fit agrees well with data up to pTa34GeV/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 0.25<pT<15GeV/c range using a single vn(pT) curve; such a description is however approximately possible for 2n5 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.

Cited by (0)

© CERN for the benefit of the ALICE Collaboration.

1

Also at Laboratoire de Physique Corpusculaire (LPC), Clermont Université, Université Blaise Pascal, CNRS-IN2P3, Clermont-Ferrand, France.

2

Also at Sezione INFN, Bologna, Italy.

3

Now at Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany.

4

Now at Laboratoire de Physique Corpusculaire (LPC), Clermont Université, Université Blaise Pascal, CNRS-IN2P3, Clermont-Ferrand, France.

5

Also at Dipartimento di Fisica dellʼUniversita, Udine, Italy.

6

Now at Sezione INFN, Turin, Italy.

7

Also at Benemérita Universidad Autónoma de Puebla, Puebla, Mexico.

8

Also at European Organization for Nuclear Research (CERN), Geneva, Switzerland.

9

Also at European Organization for Nuclear Research (CERN), Geneva, Switzerland.

10

Now at Lawrence Berkeley National Laboratory, Berkeley, CA, United States.

11

Now at Centro Fermi – Centro Studi e Ricerche e Museo Storico della Fisica “Enrico Fermi”, Rome, Italy.

12

Now at Warsaw University of Technology, Warsaw, Poland.

13

Also at Fachhochschule Köln, Köln, Germany.

14

Also at Institute of Experimental Physics, Slovak Academy of Sciences, Košice, Slovakia.

15

Also at M.V. Lomonosov Moscow State University, D.V. Skobeltsyn Institute of Nuclear Physics, Moscow, Russia.

16

Also at Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Joseph Fourier, CNRS-IN2P3, Institut Polytechnique de Grenoble, Grenoble, France.

17

Now at Dipartimento Interateneo di Fisica ‘M. Merlin’ and Sezione INFN, Bari, Italy.

18

Now at SUBATECH, Ecole des Mines de Nantes, Université de Nantes, CNRS-IN2P3, Nantes, France.

19

Also at “Vinča” Institute of Nuclear Sciences, Belgrade, Serbia.

20

Also at Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico City, Mexico.

21

Now at Wayne State University, Detroit, MI, United States.

22

Now at Department of Physics, University of Oslo, Oslo, Norway.

23

Now at Eberhard Karls Universität Tübingen, Tübingen, Germany.

24

Now at Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany.

25

Now at Institut Pluridisciplinaire Hubert Curien (IPHC), Université de Strasbourg, CNRS-IN2P3, Strasbourg, France.

26

Also at Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain.

27

Now at University of Tokyo, Tokyo, Japan.

28

Also at Nuclear Physics Institute, Academy of Sciences of the Czech Republic, Řež u Prahy, Czech Republic.

29

Also at Hua-Zhong Normal University, Wuhan, China.

30

Now at Sezione INFN, Bologna, Italy.

31

Also at Centro Fermi – Centro Studi e Ricerche e Museo Storico della Fisica “Enrico Fermi”, Rome, Italy.