paper

Long-range angular correlations of , K and p in p-Pb collisions at = 5.02 TeV

arXiv:1307.3237 · doi:10.1016/j.physletb.2013.08.024

Abstract

Angular correlations between unidentified charged trigger particles and various species of charged associated particles (unidentified particles, pions, kaons, protons and antiprotons) are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV in the transverse-momentum range GeV/. The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range . Fourier coefficients are extracted from the long-range correlations projected onto the azimuthal angle difference and studied as a function of and in intervals of event multiplicity. In high-multiplicity events, the second-order coefficient for protons, , is observed to be smaller than that for pions, , up to about GeV/. To reduce correlations due to jets, the per-trigger yield measured in low-multiplicity events is subtracted from that in high-multiplicity events. A two-ridge structure is obtained for all particle species. The Fourier decomposition of this structure shows that the second-order coefficients for pions and kaons are similar. The is found to be smaller at low and larger at higher than , with a crossing occurring at about 2 GeV. This is qualitatively similar to the elliptic-flow pattern observed in heavy-ion collisions. A mass ordering effect at low transverse momenta is consistent with expectations from hydrodynamic model calculations assuming a collectively expanding system.

26 pages, 4 captioned figures, 2 tables, authors from page 20, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/445

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