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Long-range angular correlations of pi, K and p in p--Pb collisions at sqrt(s_NN) = 5.02 TeV

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 0.3 < p_T < 4 GeV/c. The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range |eta_lab|<0.8. Fourier coefficients are extracted from the long-range correlations projected onto the azimuthal angle difference and studied as a function of $\pt$ and in intervals of event multiplicity. In high-multiplicity events, the second-order coefficient for protons, v_2^p, is observed to be smaller than that for pions, v_2^pi, up to about p_T = 2 GeV/c. 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 v_2^p is found to be smaller at low p_T and larger at higher p_T than v_2^pi, 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.
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Contributor : Emmanuelle Vernay <>
Submitted on : Friday, July 12, 2013 - 12:53:57 PM
Last modification on : Thursday, November 19, 2020 - 12:58:50 PM

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B. Abelev, N. Arbor, G. Conesa Balbastre, J. Faivre, C. Furget, et al.. Long-range angular correlations of pi, K and p in p--Pb collisions at sqrt(s_NN) = 5.02 TeV. Physics Letters B, Elsevier, 2013, 726, pp.164-177. ⟨10.1016/j.physletb.2013.08.024⟩. ⟨in2p3-00843893⟩



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